Browsing by Subject "Stress"

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Impact of housing environment and rearing condition on the immune system and welfare of laying hens
(2021) Hofmann, Tanja Melanie; Stefanski, Volker
In recent years, consumers’ interest in modern farm animal husbandry and, above all, criticism of intensive production systems that can impair animal welfare, have increased sharply. From hatch, chickens are confronted by a wide range of environmental and social stressors that may confound homeostasis and impair their health and welfare. Not being able to deal with the environment can lead to an activation of the stress system, resulting in a release of neuroendocrine signals like glucocorticoids. These have the potential to modify the immune system and alter species-specific behavior with possible detrimental impacts on animals’ health and welfare. In this context, early-life conditions play a special role as they were shown to have long-term consequences for physiology and behavior in the later life. High stocking densities which activate the hypothalamic-pituitary-adrenal-axis are said to be one of the largest welfare concerns in the poultry industry. Previous research has primarily focused on the effects of stocking density on broilers and adult laying hens, but few studies have focused explicitly on layer pullets, and none of them investigated long-term effects on the immune system. The understanding of short- and long-term consequences of environmental conditions during rearing on the immune system and behavior of layer pullets is essential for shaping an environment that avoids allostatic overload, thus promoting animal health and welfare. This doctoral thesis aimed to identify and evaluate potential immunomodulating factors in the housing environment of chickens. In order to achieve this, it summarizes and reviews important aspects of housing environments for the immune system in chickens. Furthermore, an existing flow cytometric method for the enumeration of leukocytes and discrimination of lymphocyte subsets in blood was adapted to lymphatic tissues. Moreover, short- and longterm consequences of stocking density during rearing on the immune system, stress hormone level and behavior in layer pullets were evaluated. The results are described in detail in three peer-reviewed manuscripts published in international journals. The literature analysis identified several housing conditions as immunomodulating factors. Light management was marked as an effective tool to modulate the immune response in chickens, as long light phases were demonstrated to lower adaptive cellular and humoral immune responses while certain light colors, especially of shorter wavelengths, promote some immune functions. Moreover, particularly high ammonia and hydrogen sulfide concentrations pose a threat to chickens’ health by dampening the adaptive immune response and promoting inflammation. However, the interaction between housing environment and management is complex. Depending on the type of housing form, chickens are confronted with different social and environmental challenges, which in turn can have an impact on the immune and stress system. An understanding of immunosuppressive risk factors is essential for successful poultry management aiming to optimize health, welfare and economic efficiency. To broaden the assessment of immune status for scientific purposes, new staining- and gating strategies for avian lymphatic tissues were adapted to an existing flow cytometric method for blood. The adaptation process showed that the application of already established protocols to other tissues is possible, but has to be examined carefully as tissue-specific effects or cell-preparative procedures might lead to differences in possible combinations of antibody-fluorochrome conjugates. The results of the experimental study within this doctoral thesis demonstrate for the first time that stocking density during rearing has not only short- but also long-term impacts on the immune system in laying hens. Pullets reared at high stocking densities showed stress-related alterations in immune cell numbers and higher incidences of feather pecking that manifest in the laying period. This highlights the significance of early-life conditions for immunocompetence throughout the whole production cycle. Of particular interest is that the number of gamma-delta T cells was lower in the high-density group, which has not been investigated in any stress-related studies with chickens before. The present doctoral thesis provides a significant contribution to the improvement of health and welfare in poultry farming and forms a basis for further research about long-lasting consequences of rearing conditions on the immune system, especially in laying hens.
Individual information systems
design, use, and a negative outcome in the business and private domain
(2021) Lanzl, Julia; Gimpel, Henner
Digitalization increasingly changes individuals’ business and private lives. Today, individuals build and use ever more complex individual information systems (IIS) composed of privately-owned and business-owned components. The COVID-19 pandemic has accelerated this development since individuals were forced to work from home due to the social distancing measures associated with the pandemic. The ongoing digitalization comes with great opportunities for individuals, such as higher mobility and flexibility, as well as for organizations, such as lower costs and increased productivity. However, the increased use of IIS at the workplace also bears risks for individuals. Such risks include technostress, which refers to stress that is caused by digital technologies. Technostress, in turn, can lead to health-related issues, reduced productivity, and higher turnover intentions. Thus, to leverage the positive opportunities of digitalization while reducing its associated risk of technostress, a better understanding of IIS, their use, and its effect on technostress, and of individual resources that may affect this relationship is needed. The aim of this dissertation is threefold: First, to contribute to a better understanding of layers of IIS and their different components. Second, since a negative outcome of IIS use can be technostress, this dissertation seeks to advance knowledge on technostress creators and how they can be influenced by IIS use and by various IIS characteristics. Third, this dissertation aims to reveal which resources of individuals may help mitigate technostress. This dissertation uses quantitative methods, such as online surveys and structural equation modeling, and qualitative methods, such as literature analyses and semi-structured interviews. Thereby, the methodological focus lies on quantitative data collection and analysis, while some papers use a mixed-methods approach as a combination of quantitative and qualitative methods. Chapter 2 of this dissertation aims at providing a better understanding of IIS by investigating its various components. Therefore, Chapter 2.1 conceptualizes four layers of IIS: devices, digital identities, relationships, and information. It also considers that IIS have two more or less integrated subsystems: the business information systems with business-owned components and the private information systems with privately-owned components. An empirical validation supports this conceptualization as well as the definition of integration between the two sub-systems on each of the four layers. Chapter 2.2 studies IT consumerization, which refers to the use of private IIS components in the business domain and applies a risk-benefit consideration. The results imply that benefits of consumerization of IT services, such as better functionalities of a private IT service outweigh risks, such as the threat of sanctions for the use of private IT services. Chapter 3 focuses on technostress as a negative outcome of the increased IIS use. Chapter 3.1 analyzes how IT consumerization is related to the technostress creator unreliability of digital technologies. The results reveal a positive relationship between IT consumerization and unreliability and show that unreliability is perceived higher when the IT portfolio integration and the individual’s computer self-efficacy are low. Chapter 3.2 proceeds with studying characteristics of digital technologies and how these are related to technostress. It presents ten characteristics that are associated with at least one technostress creator. Chapter 3.3 extends the concept of technostress and introduces a framework of twelve different technostress creators, reveals four second-order factors underlying the twelve technostress creators, and brings them into relation with work- and health-related effects. Chapter 4 also deals with technostress and investigates resources to mitigate technostress. Chapter 4.1 focuses on organizational measures and finds different relationships of the investigated measures with different technostress creators. While some of the technostress creators can be inhibited by the implementation of organizational measures, others are found to be even intensified by the organizational measures. Chapter 4.2 focuses on social mechanisms that function as technostress inhibitors. Findings differ between technostress creators and the investigated social support dimensions. Furthermore, the results highlight the fact that some of the social support dimensions gain even greater importance in light of increasing telework. In summary, this dissertation provides new insights into IIS and their use, the emergence of technostress in digitalized workplaces, and organizational as well as social mechanisms that help mitigate technostress. Hence, this dissertation supports current efforts in both research and practice to reduce technostress while leveraging the positive opportunities of workplace digitalization.
Laterality in horse training: psychological and physical balance and coordination and strength rather than straightness
(2022) Krueger, Konstanze; Schwarz, Sophie; Marr, Isabell; Farmer, Kate
For centuries, a goal of training in many equestrian disciplines has been to straighten the horse, which is considered a key element in achieving its responsiveness and suppleness. However, laterality is a naturally occurring phenomenon in horses and encompasses body asymmetry, motor laterality and sensory laterality. Furthermore, forcibly counterbalancing motor laterality has been considered a cause of psychological imbalance in humans. Perhaps asymmetry and laterality should rather be accepted, with a focus on training psychological and physical balance, coordination and equal strength on both sides instead of enforcing “straightness”. To explore this, we conducted a review of the literature on the function and causes of motor and sensory laterality in horses, especially in horses when trained on the ground or under a rider. The literature reveals that body asymmetry is innate but does not prevent the horse from performing at a high level under a rider. Motor laterality is equally distributed in feral horses, while in domestic horses, age, breed, training and carrying a rider may cause left leg preferences. Most horses initially observe novel persons and potentially threatening objects or situations with their left sensory organs. Pronounced preferences for the use of left sensory organs or limbs indicate that the horse is experiencing increased emotionality or stress, and long-term insufficiencies in welfare, housing or training may result in left shifts in motor and sensory laterality and pessimistic mentalities. Therefore, increasing laterality can be regarded as an indicator for insufficiencies in housing, handling and training. We propose that laterality be recognized as a welfare indicator and that straightening the horse should be achieved by conducting training focused on balance, coordination and equal strength on both sides.
Negative affective states in customers’ service experience
investigating antecedents and mitigations
(2019) Haager, Stephanie; Büttgen, Marion
Previous research has provided various insights into the potential benefits and competitive advantages of customer participation (Bendapudi and Leone 2003). For instance, customer participation can lower production costs and improve productivity (Lovelock and Young 1979; Mills and Morris 1986), service quality, customer satisfaction (Bendapudi and Leone 2003; Chan et al. 2010; Dong et al. 2015), and opportunities for promotion (Bettencourt 1997). Hence, many companies create a new customer experience by making the customer a co-creator of value (Ramaswamy and Gouillart 2010). However, observing people trying to print their own luggage tags and checking in at an airport or assembling IKEA furniture reveals emotions that are not always positive. Customers appear to be overtaxed, irritated, unhappy, and distressed. This phenomenon is especially relevant for services that are crucial for customers and that cause them to feel some kind of pressure (e.g., time), that are hard to understand, or are in any way upsetting. For instance, in one of their studies, Berry et al. (2015) found that patients in hospitals experienced such stress due to the service process and newspapers often also report on the problem of customers feeling helpless at banks (Adamu 2015). Attributable to the growing number of tasks that customers have to fulfill, yet, they are not driven by failures in the process but by stressors within the service process. Such stressors could arise from industry-specific knowledge that customers often do not have (e.g., financial expertise), the high relevance of the service to a customer’s life (e.g., medical services), or high time pressure (e.g., the need to catch a flight). However, organizations might not be aware of such stressors, and research about negative emotions, particularly stress due to physical and mental overload and strain in customer participation, is lacking. Service organizations, however, might benefit from such research, as managers must be aware of potential stressors and the possibility that customers could become stressed due to the characteristics of the service itself. Greater knowledge in this area would enable managers to respond to customer stress appropriately, e.g., by altering the service design or process and by training their employees to intervene when necessary. This thesis seeks to fill in this gap within two empirical studies (chapter 2 and 3). As a means of investigating negative customer emotions in services with flawless delivery, customer participation stress (CPS) is introduced as a new construct to service marketing research. The definition of CPS builds on established definitions of stress from general and organizational psychology and links them to the behavioral aspects of customer participation. While CPS is a negative emotion that occurs within the service process, some services are affected by negative emotions that have already emerged before the actual service encounter and/or are the initial reason the customer has come to the service provider. These services, such as medical or funeral services, can be summarized as negative services (Dasu and Rao 1999; Morgan and Rao 2006). It might be a challenge for service organizations to actively engage customers in such services, yet their professional reputations are vital to their ability to remain in business; methods of how such service providers may increase customer engagement are outlined in chapter 3. While previous studies have presented valuable insights into positive emotions in the customer experience, negative emotions due to service failure, and the service process of negative services, research to date has not covered knowledge about negative customer emotions in flawless customer experiences with a focus on jointly created value of employee and customer and a comprehensive definition and boundaries of negative services. This thesis seeks to fill in these gaps with three distinct but related studies, two quantitative and one conceptual; answering to the following research questions: 1. Which demands and resources of the participation process cause CPS and how does CPS influence customer participation behavior? 2. What are the consequences of CPS and how do they influence customers’ evaluation of a service? 3. How can the characteristics of the participation process and customers’ predispositions mitigate unwanted psycho-physical and behavioral outcomes of CPS? 4. What characterizes negative services and how can providers of such service be more successful by engaging customers?
Non-invasive welfare evaluations in horses
the usefulness of laterality
(2020) Marr, Isabell; Stefanski, Volker
Animal welfare is becoming increasingly important, especially for animal owners. In particular, prey animals such as horses generally suffer in silence. To improve the evaluation of animal welfare in practice and to simplify it in scientific research, new welfare indicators are needed that are easier to assess, less time consuming, and repeatable. Therefore, this thesis aimed to investigate laterality as a welfare indicator that could meet these requirements. Domestic horses were used as model organisms as they display sensory and motor laterality on individual and/or population level; their sensory organs are placed laterally, non-invasive stress hormone analysis is already well-established, as a highly social animal that evolved on open ranges it is prone to suffering from inappropriate human management regimes, and it displays various stress responses. In STUDY it could be demonstrated that a shift to an enhanced preference for the right brain hemisphere was in line with increased stress hormone concentrations in faeces. Sensory laterality and motor laterality measured while grazing, shifted to the left when natural needs were restricted by a change from group to individual housing. Sensory laterality changed immediately after the change of housing conditions, whereas the motor laterality changed with a time delay of one week. STUDY 2 demonstrated that motor laterality measured as initial forelimb use correlated with the cognitive bias (welfare indicator). Right-sided horses were faster to approach an ambiguous stimulus and therefore displayed a positive cognitive bias. But neither motor laterality, measured through grazing stance, nor sensory laterality were related to cognitive bias. STUDY 3 demonstrated that a preference for left side sensory organ use is not only evident in negative contexts but also in positive contexts, because the horses also preferred their left side during affiliative interactions that are assumed to induce positive emotions. This study demonstrated that not only the direction of shift in laterality, but also the context of the shift, should be recorded to reliably identify poor or good welfare. Therefore, it is recommended that additional stress parameters be applied to reliably evaluate animal welfare. STUDY 4 investigated whether the sampling and analysis of faecal stress hormones and immunoglobulin A could be simplified by applying a novel conservation method. Often it is not possible to immediately freeze the faecal samples and/or the transportation to the lab is lengthy. The study demonstrated that faecal samples can be dried a closed system such as an air-tight tube containing silica gel. The samples were dried within 24 hours, as fast as in controlled air-drying conditions at room temperature. The new and simpler drying method prevented the stress hormones (glucocorticoid metabolites) from enzymatic degradation and conserved them, demonstrated by the fact that the detectable concentration remained unchanged. In contrast, immunoglobulin A showed a reduction in the detectable concentration. Therefore, if possible, the conservation of faecal samples should be avoided when immunoglobulin A is to be analysed, although it would be possible to apply an extrapolation to attain fairly reliable results. This new drying method will simplify research on wild horses into the type of stressors they are confronted with, the impact of natural stressors, and effect of stressors on, for example, their laterality in comparison with domestic horses. STUDY 5 investigated whether the strength of laterality provides insight into basal physiological and immunological status, stress response, stress reactivity, or cognitive bias. Only a correlation between age and the strength of laterality was found, with strength of laterality increasing with age. However, age could explain only 30 per cent of the inter-individual variation in strength of laterality. The results demonstrated that the strength of laterality is not a reliable indicator of animal welfare. The direction of laterality may be of greater importance. Altogether, it was demonstrated that laterality is a promising, reliable, repeatable, and objective indictor of animal welfare, which is quick and easy to asses, and inexpensive. Like other well-established welfare and stress indicators, laterality has its limitations. Therefore, it is recommended that other welfare indicator should be simultaneously assessed and changes in laterality recorded, as different traits and personalities result in a high inter-individual variation in base laterality indices. Possible influences and correlations between emotional processing and cerebral lateralization are discussed. Nonetheless, further research is needed to establish a more reliable measurement of motor laterality, and to better understand the relationship between emotional processing and lateralization, as well as possible influencing factors.
Das Potenzial der teilmobilen Schlachtung von Rindern im Herkunftsbetrieb
Stressbelastung und Fleischqualität
(2022) Zeidler, Johannes
The industrialization of animal husbandry and the focus on large production volumes have led to the killing of farm animals taking place almost exclusively in what are now a few large slaughterhouses. Of the approximately 3.4 Mio cattle slaughtered in Germany in 2019, nearly 78% are slaughtered in Germanys 10 largest slaughterhouses. Local butchers and small slaughterhouses often cannot comply with the strict legal hygiene regulations. The animals must therefore be transported alive, where loading, the journey, the foreign environment, the separation from the herd and the meeting with unfamiliar animals and humans, are known to cause stress and as well have negative impacts on meat quality. Since the revision of the EU regulation 853/2004 in 2021, slaughter at the farm of origin is now considered an official slaughter method. Although research focussing on slaughtering cattle on the farm of origin using captive bold stunning is missing, meat of cattle slaughtered via gunshot on pasture tends to be more tender and stress levels can be reduced in comparison to cattle slaughtered in the slaughterhouse. This leads to the assumption that also slaughtering cattle on the farm of origin, using captive bolt stunning, should result in higher meat quality and reduce stress prior to slaughter. For this purpose, this study examined 27 cattle from seven different farms slaughtered either on farm of origin using captive bolt stunning, via gunshot or in commercial slaughterhouses. Meat quality parameters and stress indicators were assessed to evaluate these three slaughter methods from a meat quality and an animal welfare perspective Based on the cortisol levels in the blood of exsanguination, no significant differences in the stress levels of the different slaughter methods could be determined. Nevertheless, tendencies towards less stressed animals with slaughtered via gunshot and slaughtered on the farm of origin using captive bolt stunning compared to the slaughterhouse could be revealed. As large variances of cortisol concentrations were measured within cattle slaughtered on farm of origin, stress level seems to depend on the individual slaughtering and preparing procedure. Further research is needed to improve and give recommendations for practical implementation of this method taking different farm structures into account. Quality parameters were not unambiguous. A significant effect of the slaughter method could only be found on ultimate pH-value and redness (a* L*a*b* System). Contrary to our expectations, ultimate pH-value was significantly lower in meat of cattle slaughtered on farm of origin using captive bolt stunning than in meat of cattle slaughtered via gunshot. Moreover, cattle slaughtered on farm of origin using captive bold, had significantly redder meat than cattle slaughtered via gunshot This contradicts the assumption that more stress leads to less red meat. However, it is consistent with the lower pH values of meat from cattle slaughtered with bolt stunning at the farm of origin, because low pH values lead to redder meat. Exploratory results comparing only meat from commercial slaughterhouses with meat from cattle slaughtered on farm using captive bolt stunning show clearer trends. Lower ultimate pH-values, as well as trends towards more tender and juicy meat could be found in cattle slaughtered on farm. To ensure these results and to evaluate meat quality according to different slaughter methods in upcoming research, either environmental effects should be reduced, or the dataset must be larger.
Stress hormone-induced immunomodulation and interplay between immune cells and bacteria in response to stress hormones in domestic pigs
(2020) Reiske, Lena; Stefanski, Volker
The two main endocrine systems involved in the regulation of stress reactions are the HPA axis, leading to the synthesis of glucocorticoids like cortisol or corticosterone, and the SAM axis, whose activation is associated with the release of the catecholamines adrenaline and noradrenaline. These stress hormones modulate the function of the immune system. Although pigs in modern husbandry systems face many stressors, the consequences of elevated plasma stress hormone levels on porcine immune cell numbers and functionality are insufficiently resolved. While some research on glucocorticoid effects has been conducted, data on many parameters are missing and catecholamines have not been studied systematically in the pig, yet. It is known that stress can negatively affect pigs’ resistance to infections like salmonellosis, but the underlying mechanisms are still subject to intense research efforts, with new perspectives arising since the discovery of interkingdom-signalling and microbial catecholamine perception. The aim of this thesis was to determine the effects of cortisol, adrenaline and noradrenaline on porcine immune cell functionality and the blood numbers of different leukocyte subsets. Furthermore, the interplay of immune cells and Salmonella Typhimurium under the influence of catecholamines was investigated. Adult male castrated pigs were surgically equipped with indwelling catheters to enable stress-free blood collection and intravenous application of hormones. In an initial experiment, the effects of in vitro stress hormone treatment on lymphocyte proliferation and the production of the proinflammatory cytokine TNFa were described. Cortisol reduced both proliferation and number of TNFa producers. Both catecholamines caused an increased lymphocyte proliferation at low concentrations whereas noradrenaline drastically decreased proliferation at high concentrations. While noradrenaline had no impact on TNFa producers, they were reduced in gd T cells and monocytes upon adrenaline addition. Overall, the effects were comparable to humans in terms of direction and dose but there were some disparities regarding adrenaline. In the second part of the project, the impact of in vivo stress hormone administration on immune cell numbers and functionality was examined by infusion for 48h. Cortisol and noradrenaline led to a decreased lymphocyte proliferation but to a variable extent and all three hormones promoted phagocytic function of innate immune cells. Cortisol caused a marked increase of neutrophil numbers while almost all other cell types declined strongly. For most cell types, noradrenaline exerted similar effects but solely after 2h whereas cortisol-induced alterations lasted the whole treatment period. Adrenaline effects were mostly reduced to CD8- T cells, which were reduced at first but increased after 24h. A sharp peak in NK cell numbers after 2h adrenaline infusion is particularly noteworthy and resembles findings from rodent and human studies. Overall, both hormone groups led to a shift from adaptive to innate immunity, underpinning the picture of a promotion of fast and unspecific defence systems to respond to threats in stressful situations. In a third study, S. Typhimurium was grown in the presence of catecholamines to determine the effects of supernatants from these cultures on porcine immune cell function. Both lymphocyte proliferation and TNFα production were hampered substantially, as opposed to the findings on catecholamine effects in the first experiment. It was demonstrated that these effects were not caused by catecholamines or their oxidation products and the formation of a so-far unknown immunosuppressive substance by catecholamine-primed bacteria was assumed. The results contribute to a better understanding of the increased susceptibility to infection in stressed animals and reveal a new dimension of cross-species communication. Finally, the results of the present thesis were discussed regarding their comparability to studies in humans and rodents and previous stress experiments in pigs. Furthermore, the effects of acute and chronic stress as well as different coping styles that are characterised by a SAM or HPA predominance on animal welfare and pig health were discussed, based on the endocrine mechanisms investigated in the present thesis. Possible implications of enhanced glucocorticoid and catecholamine levels for practical pig husbandry were given. Lastly, suggestions for future research to further elucidate the impact of stress hormones on the porcine immune system and the interplay with pathogenic bacteria were made.
Stress management and coping using smartphones by mothers of young children
(2021) Wolfers, Lara N.; Utz, Sonja
Being a parent of young children is associated with both joy and stress. High parental stress was shown to be associated with decreased parental wellbeing and negative child outcomes. Thus, it is important that parents successfully cope with stress. Research has shown that becoming a parent often results in constraints on time allocation and a perceived state of isolation, making it harder to cope with stress. Smartphones might be a useful tool for parental stress management. For most parents, smartphones are always and easily accessible. Moreover, smartphones can provide many resources such as social support and information and can be used for short periods. Accordingly, first studies show that parents often use their smartphones to cope with stress. However, parental smartphone use has been widely problematized in academic and public discussions because smartphones are said to distract parents from interacting with their children. Research on how parents use smartphones to their benefit is still limited. Moreover, we do not know yet whether and under what circumstances coping using smartphones effectively reduces parental stress. To fill this knowledge gap, I examined in my dissertation how mothers of young children use their smartphones for coping with stress and under what circumstances coping using smartphones is effective. As mothers are still the primary caregivers, my dissertation mainly focuses on mothers. In a first theoretical step, I conducted a systematic scoping review summarizing and integrating the previous literature on media use for coping. Many studies assessed how media are used for coping. However, the literature had not clearly identified where media have their place in stress management models. In the scoping review, I suggested placing media in the transactional model of stress and coping by differentiating between coping strategies, such as social support or distraction and coping tools, such as talking to a friend or using a smartphone. When confronted with a stressful encounter, individuals choose a combination of coping tools and coping strategies to cope with stress. The fit of this combination with the situational circumstances determines whether the coping efforts are successful. Based on this conceptualization, I conducted a qualitative focus groups study and a quantitative experience sampling study (ESS). In the focus group study, building on a synthesis of the literature on digital media use for parenting and smartphone use while parenting, I interviewed parents in a medium-sized city and a parent-child health retreat clinic about how they use their smartphones for stress management. In the ESS, I additionally drew on theoretical conceptualizations from mobile communication and digital wellbeing research. Over 200 mothers filled in four questionnaires a day for one week and answered questions about a stressful situation that had happened in the last two hours. Both studies showed that when mothers are in stressful situations with their children, they mainly use their phones to distract themselves from the stressful encounter and to find information and support. In the focus groups study, parents reported many instances in which they successfully used their phones for stress coping. In the ESS, mothers, however, experienced a smaller stress decrease in stressful situations in which they used their phone than in situations involving no phone use. Using positive phone content, though, was related to increased coping effectiveness. My dissertation also demonstrated that social norms around maternal smartphone use play an important role when mothers use their phones for coping with stress. To explore this, I suggested a social constructivist viewpoint on media use and media effects. This viewpoint posits that the perception of and feelings around ones own media use are just as important for media effects as characteristics of objectively measurable media use, such as usage time. Further, I argue that these media use perceptions are influenced by what others say about media use and are, thus, socially constructed. Confirming the value of this viewpoint, I show in the ESS that mothers who perceived stronger injunctive norms against parental phone use experienced increased guilt when they used their phone for stress coping. Feelings of guilt around phone use in turn were related to a diminished coping effectiveness. Overall, my dissertation shows that by using positive content, mothers can use their smartphones to their benefit when they are confronted with stressful situations. Negative social norms against parental smartphone use can, by inducing guilt, be associated with diminished coping effectiveness when mothers use their phone to cope with stress. Therefore, academic and public discussions around smartphone use should consider the benefits of smartphone use for parents so that a more nuanced debate does not lead to social pressure and feelings of guilt among parents.
Toward effects of hydrophobicity on biosurfactant production by Bacillus subtilis isolates from crude-oil-exposed environments
(2024) Hashemi, Seyedeh Zahra; Fooladi, Jamshid; Vahidinasab, Maliheh; Hubel, Philipp; Pfannstiel, Jens; Pillai, Evelina; Hrenn, Holger; Hausmann, Rudolf; Lilge, Lars
Background: Due to their structural features, biosurfactants reveal promising physicochemical properties, making them interesting for various applications in different fields, such as the food, cosmetics, agriculture, and bioremediation sectors. In particular, the bioproduction of surfactin, one of the most potent microbially synthesized biosurfactant molecules, is of great interest. However, since the wild-type productivities are comparably low, stimulatory environmental conditions have to be identified for improved bioproduction This study aims to find a correlation between the hydrophobicity and production of the biosurfactant surfactin by B. subtilis isolates from crude-oil-contaminated soil and water. Methods: The surfactin production yield was characterized in adapted batch cultivations using high-performance thin-layer liquid chromatography (HPTLC). Defined hydrophobic environmental conditions were achieved by supplementation with hexadecane or polystyrene beads, and the effects on biosurfactant production were measured. Adaptations at the protein level were analyzed using mass spectrometry measurements. Results: The correlation between hydrophobicity and surfactin production was characterized using Bacillus subtilis strains ZH1 and P7 isolated from crude-oil-contaminated soil and water. Since these isolates show the biodegradation of crude oil and hexadecane as hydrophobic substrates, respectively, a first-time approach, using polystyrene beads, was applied to provide a hydrophobic environment. Interestingly, contrary to popular opinion, reduced biosurfactant production was determined. Using mass spectrometric approaches, the physiological effects of co-cultivation and the cellular response at the protein level were investigated, resulting in altered quantities of stress proteins and proteins involved in the carbon metabolism counter to polystyrene beads. Conclusions: Contrary to common opinion, increasing hydrophobicity does not have a stimulating effect, and even reduces the effect on the bioproduction of surfactin as the main biosurfactant using selected B. subtilis strains.