A Shift to Human Body Temperature (37°C) Rapidly Reprograms Multiple Adaptive Responses in Escherichia coli That Would Facilitate Niche Survival and Colonization

FdeC expression regulates motility and adhesion of the avian pathogenic Escherichia coli strain IMT5155

Adaptation of avian pathogenic E. coli (APEC) to changing host environments including virulence factors expression is vital for disease progression. FdeC is an autotransporter adhesin that plays a role in uropathogenic Escherichia coli (UPEC) adhesion to epithelial cells. Expression of fdeC is known to be regulated by environmental conditions in UPEC and Shiga toxin-producing E. coli (STEC). The observation in a previous study that an APEC strain IMT5155 in which the fdeC gene was disrupted by a transposon insertion resulted in elevated adhesion to chicken intestinal cells prompted us to further explore the role of fdeC in infection. We found that the fdeC gene prevalence and FdeC variant prevalence differed between APEC and nonpathogenic E. coli genomes. Expression of the fdeC gene was induced at host body temperature, an infection relevant condition. Disruption of fdeC resulted in greater adhesion to CHIC-8E11 cells and increased motility at 42 °C compared to wild type (WT) and higher expression of multiple transporter proteins that increased inorganic ion export. Increased motility may be related to increased inorganic ion export since this resulted in downregulation of YbjN, a protein known to supress motility. Inactivation of fdeC in APEC strain IMT5155 resulted in a weaker immune response in chickens compared to WT in experimental infections. Our findings suggest that FdeC is upregulated in the host and contributes to interactions with the host by down-modulating motility during colonization. A thorough understanding of the regulation and function of FdeC could provide novel insights into E. coli pathogenesis.

Extracellular DNAses Facilitate Antagonism and Coexistence in Bacterial Competitor-Sensing Interference Competition

Over the last 4 decades, the rate of discovery of novel antibiotics has decreased drastically, ending the era of fortuitous antibiotic discovery. A better understanding of the biology of bacteriogenic toxins potentially helps to prospect for new antibiotics. To initiate this line of research, we quantified antagonists from two different sites at two different depths of soil and found the relative number of antagonists to correlate with the bacterial load and carbon-to-nitrogen (C/N) ratio of the soil. Consecutive studies show the importance of antagonist interactions between soil isolates and the lack of a predicted role for nutrient availability and, therefore, support an in situ role in offense for the production of toxins in environments of high bacterial loads. In addition, the production of extracellular DNAses (exDNases) and the ability to antagonize correlate strongly. Using an in domum-developed probabilistic cellular automaton model, we studied the consequences of exDNase production for both coexistence and diversity within a dynamic equilibrium. Our model demonstrates that exDNase-producing isolates involved in amensal interactions act to stabilize a community, leading to increased coexistence within a competitor-sensing interference competition environment. Our results signify that the environmental and biological cues that control natural-product formation are important for understanding antagonism and community dynamics, structure, and function, permitting the development of directed searches and the use of these insights for drug discovery. IMPORTANCE Ever since the first observation of antagonism by microorganisms by Ernest Duchesne (E. Duchesne, Contribution à l'étude de la concurrence vitale chez les microorganisms. Antagonism entre les moisissures et les microbes, These pour obtenir le grade de docteur en medicine, Lyon, France, 1897), many scientists successfully identified and applied bacteriogenic bioactive compounds from soils to cure infection. Unfortunately, overuse of antibiotics and the emergence of clinical antibiotic resistance, combined with a lack of discovery, have hampered our ability to combat infections. A deeper understanding of the biology of toxins and the cues leading to their production may elevate the success rate of the much-needed discovery of novel antibiotics. We initiated this line of research and discovered that bacterial reciprocal antagonism is associated with exDNase production in isolates from environments with high bacterial loads, while diversity may increase in environments of lower bacterial loads.

Investigation of the Relation between Temperature and M13 Phage Production via ATP Expenditure

M13 bacteriophage is a promising biomolecule capable of various bionano and material science applications. The biomaterial can self-assemble into matrices to fabricate bioscaffolds using high phage concentration and high phage purity. Previous studies aimed to acquire these conditions in large-scale phage production and have identified the optimal culture temperature range at 28–31 °C. However, explanations as to why this temperature range was optimal for phage production is absent from the work. Therefore, in this study, we identified the relation between culture temperature and M13 phage production using ATP expenditure calculations to comprehend the high yield phage production at the optimal temperature range. We extended a coarse-grained model for the evaluation of phage protein and ribosomal protein synthesis with the premise that phage proteins (a ribosomal protein) are translated by bacterial ribosomes in E. coli through expenditure of ATP energy. By comparing the ATP energy for ribosomal protein synthesis estimated using the coarse-grained model and the experimentally calculated ATP expenditure for phage production, we interpreted the high phage yield at the optimal temperature range and recognized ATP analysis as a reasonable method that can be used to evaluate other parameters for phage production optimization.

A Culture-Based Study of Micromycetes Isolated from the Urban Nests of Grey Heron (Ardea cinerea) in SW Poland

Simple Summary

Fungi inhabiting bird nests may pose a serious threat to living organisms. Therefore, the main goal of the study was to identify cultivable fungi in the nest of grey heron (Ardea cinerea) located near the city centre of Wrocław (Poland). Overall, 10 different fungal species were obtained which were both cosmopolitan and potentially hazardous to humans, homoiothermous animals and plants. The greatest number of fungal species was obtained from the nest fragments with visible fungal growth, and the least from western conifer seed bugs (Leptoglossus occidentalis) inhabiting the nests. The damp chamber allowed isolation of Aspergillus fumigatus, Penicillium coprophilum, and P. griseofulvum as directly related to the occurrence of visible fungal growth on plant fragments of grey heron nests.

Abstract

There are many positive relationships between micromycetes and birds: They can spread fungal spores, and fungi facilitate cavity woodpecker excavation by preparing and modifying excavation sites. In turn, bird nests are mainly a source of potentially zoopathogenic fungi. The Wrocław city centre hosts the biggest grey heron breeding colony in Poland with at least 240 breeding birds pairs. To assess the possible public health risks associated with bird nests, the goal of the present study was to identify cultivable fungi present in the nests of grey herons (Ardea cinerea) in Wrocław. Additionally, attempts were made to determine whether the obtained species of fungi may pose a potential threat to animal health. Fungi were cultured at 23 and 37 ± 0.5 °C, and identified based on phenotypic and genotypic traits. Moreover, during routine inspection, visible fungal growth in some of the nests was found. Overall, 10 different fungal species were obtained in the study (Alternaria alternata, Aspergillus fumigatus, Botryotrichum piluliferum, Cladosporium cladosporioides, Epicoccum layuense, Mucor circinelloides, M.hiemalis, Penicillium atramentosum, P.coprophilum, and P.griseofulvum). They are both cosmopolitan species and a source of potential threat to humans, homoiothermous animals and plants. The greatest number of fungal species was obtained from the nest fragments with visible fungal growth incubated at 23 °C, and the least from western conifer seed bugs (Leptoglossus occidentalis) inhabiting the nests. The species such as A. fumigatus, P. coprophilum, and P.griseofulvum can be directly related to the occurrence of visible fungal growth on plant fragments of grey heron’s nests.

A Novel Locally c-di-GMP-Controlled Exopolysaccharide Synthase Required for Bacteriophage N4 Infection of Escherichia coli

A major target of c-di-GMP signaling is the production of biofilm-associated extracellular polymeric substances (EPS), which in Escherichia coli K-12 include amyloid curli fibers, phosphoethanolamine-modified cellulose, and poly-N-acetylglucosamine. However, the characterized c-di-GMP-binding effector systems are largely outnumbered by the 12 diguanylate cyclases (DGCs) and 13 phosphodiesterases (PDEs), which synthetize and degrade c-di-GMP, respectively. E. coli possesses a single protein with a potentially c-di-GMP-binding MshEN domain, NfrB, which-together with the outer membrane protein NfrA-is known to serve as a receptor system for phage N4. Here, we show that NfrB not only binds c-di-GMP with high affinity but, as a novel c-di-GMP-controlled glycosyltransferase, synthesizes a secreted EPS, which can impede motility and is required as an initial receptor for phage N4 infection. In addition, a systematic screening of the 12 DGCs of E. coli K-12 revealed that specifically DgcJ is required for the infection with phage N4 and interacts directly with NfrB. This is in line with local signaling models, where specific DGCs and/or PDEs form protein complexes with particular c-di-GMP effector/target systems. Our findings thus provide further evidence that intracellular signaling pathways, which all use the same diffusible second messenger, can act in parallel in a highly specific manner. IMPORTANCE Key findings in model organisms led to the concept of "local" signaling, challenging the dogma of a gradually increasing global intracellular c-di-GMP concentration driving the motile-sessile transition in bacteria. In our current model, bacteria dynamically combine both global and local signaling modes, in which specific DGCs and/or PDEs team up with effector/target systems in multiprotein complexes. The present study highlights a novel example of how specificity in c-di-GMP signaling can be achieved by showing NfrB as a novel c-di-GMP binding effector in E. coli, which is controlled in a local manner specifically by DgcJ. We further show that NfrB (which was initially found as a part of a receptor system for phage N4) is involved in the production of a novel exopolysaccharide. Finally, our data shine new light on host interaction of phage N4, which uses this exopolysaccharide as an initial receptor for adsorption.