Interference Competition Among Household Strains of Pseudomonas

Environmental Factors Affecting the Diversity and Composition of Environmental Microorganisms in the Shaoxing Rice Wine Producing Area

Shaoxing rice wine is a notable exemplar of Chinese rice wine. Its superior quality is strongly correlated with the indigenous natural environment. The results indicated that Firmicutes (75%), Actinobacteria (15%), Proteobacteria (5%), and Bacteroidetes (3%) comprised the prevailing bacterial groups. Among the main bacterial genera, Lactobacillus was the most abundant, accounting for 49.4%, followed by Lactococcus (11.9%), Saccharopolyspora (13.1%), Leuconostoc (4.1%), and Thermoactinomyces (1.1%). The dominant fungal phyla were Ascomycota and Zygomycota. Among the dominant genera, Saccharomyces (59.3%) prevailed as the most abundant, followed by Saccharomycopsis (10.7%), Aspergillus (7.1%), Thermomyces (6.2%), Rhizopus (4.9%), Rhizomucor (2.2%), and Mucor (1.3%). The findings demonstrate that the structure of the bacterial and fungal communities remains stable in the environment, with their diversity strongly influenced by climatic conditions. The continuous fluctuations in environmental factors, such as temperature, air pressure, humidity, rainfall, and light, significantly impact the composition and diversity of microbial populations, particularly the dominant bacterial community.

Pyocin-mediated antagonistic interactions in Pseudomonas spp. isolated in James Ross Island, Antarctica

Interactions within bacterial communities are frequently mediated by the production of antimicrobial agents. Despite the increasing interest in research of new antimicrobials, studies describing antagonistic interactions among cold-adapted microorganisms are still rare. Our study assessed the antimicrobial interactions of 36 Antarctic Pseudomonas spp. and described the genetic background of these interactions in selected strains. The overall bacteriocinogeny was greater compared to mesophilic Pseudomonas non-aeruginosa species. R-type tailocins were detected on transmission electron micrographs in 16 strains (44.4%); phylogenetic analysis of the corresponding gene clusters revealed that the P. prosekii CCM 8878 tailocin was related to the Rp3 group, whereas the tailocin in Pseudomonas sp. CCM 8880 to the Rp4 group. Soluble antimicrobials were produced by eight strains (22.-2%); gene mining found pyocin L homologues in the genomes of P. prosekii CCM 8881 and CCM 8879 and pyocin S9-like homologues in P. prosekii CCM 8881 and Pseudomonas sp. CCM 8880. Analysis of secretomes confirmed the production of all S- and L-type pyocin genes. Our results suggest that bacteriocin-based inhibition plays an important role in interactions among Antarctic soil bacteria, and these native, cold-adapted microorganisms could be a promising source of new antimicrobials.

Spatial structure maintains diversity of pyocin inhibition in household Pseudomonas aeruginosa

Nearly all bacteria produce narrow-spectrum antibiotics called bacteriocins. Studies have shown that bacteriocins can mediate microbial interactions, but the mechanisms underlying patterns of inhibition are less well understood. We assembled a spatially structured collection of isolates of Pseudomonas aeruginosa from bathroom and kitchen sink drains in nine households. Growth inhibition of these P. aeruginosa by bacteriocins, known as pyocins in this species, was measured using pairwise inhibition assays. Carbon source usage of these isolates was measured, and genetic distance was estimated using multilocus sequencing. We found that as the distance between sites of isolation increased, there was a significantly higher probability of inhibition, and that pyocin inhibition and susceptibility vary greatly among isolates collected from different houses. We also detected support for other mechanisms influencing diversity: inhibition outcomes were influenced by the type of drain from which isolates were collected, and while we found no indication that carbon source utilization influences inhibition, inhibition was favoured at an intermediate genetic distance. Overall, these results suggest that the combined effects of dispersal limitation among sites and competitive exclusion within them maintain diversity in pyocin inhibition and susceptibility phenotypes, and that additional processes such as local adaptation and effects of phylogenetic distance could further contribute to spatial variability.

Prevalence of bacteriocins and their co-association with virulence factors within Pseudomonas aeruginosa catheter isolates

Urinary tract infections represent common nosocomial infectious diseases. Bacteriocin production has been recently described as a putative virulence factor in these infections but studies focusing particularly on Pseudomonas aeruginosa are not available. Therefore, we assessed the prevalence of the bacteriocin genes, their co-occurrence and their co-association with previously detected virulence factors in a set of 135 P. aeruginosa strains from catheter-associated urinary tract infections (CAUTIs). The overall bacteriocinogeny reached 96.3 % with an average of 3.6 genes per strain. The most frequently detected determinants were the encoded pyocins S4 (76.3 %), R (69.6 %), and S2 (67.4 %). A statistically significant co-occurrence and a negative relationship were observed between several pyocin types. Particular pyocins exhibited associations with biofilm formation, production of pyochelin, pyocyanin, antibiotic-degrading enzymes, overall strain susceptibility and resistance, and motility of the strain. Co-occurrence of the pyocins S2 and S4 (p<<0.0001; Z = 13.15), both utilizating the ferripyoverdine receptor FpvAI, was found but no relation to pyoverdine production was detected. A negative association (p = 0.0047; Z=-2.83) was observed between pyochelin and pyocin S5 utilising the ferripyochelin receptor FptA. Pairwise assays resulted in 52.1 % inhibition which was equally distributed between soluble and particle types of antimicrobials. In conclusion, pyocin determinants appear to be important characteristics of CAUTI-related P. aeruginosa isolates and could contribute to their urovirulence.

Strain variability in biofilm formation: A food safety and quality perspective

The inherent differences in microbial behavior among identically treated strains of the same microbial species, referred to as "strain variability", are regarded as an important source of variability in microbiological studies. Biofilms are defined as the structured multicellular communities with complex architecture that enable microorganisms to grow adhered to abiotic or living surfaces and constitute a fundamental aspect of microbial ecology. The research studies assessing the strain variability in biofilm formation are relatively few compared to the ones evaluating other aspects of microbial behavior such as virulence, growth and stress resistance. Among the available research data on intra-species variability in biofilm formation, compiled and discussed in the present review, most of them refer to foodborne pathogens as compared to spoilage microorganisms. Molecular and physiological aspects of biofilm formation potentially related to strain-specific responses, as well as information on the characterization and quantitative description of this type of biological variability are presented and discussed. Despite the considerable amount of available information on the strain variability in biofilm formation, there are certain data gaps and still-existing challenges that future research should cover and address. Current and future advances in systems biology and omics technologies are expected to aid significantly in the explanation of phenotypic strain variability, including biofilm formation variability, allowing for its integration in microbiological risk assessment.

Life in the cystic fibrosis upper respiratory tract influences competitive ability of the opportunistic pathogen Pseudomonas aeruginosa

Understanding characteristic differences between host-associated and free-living opportunistic pathogens can provide insight into the fundamental requirements for success after dispersal to the host environment, and more generally into the ecological and evolutionary processes by which populations respond to simultaneous selection on complex interacting traits. We examined how cystic fibrosis (CF)-associated and environmental isolates of the opportunistic pathogen Pseudomonas aeruginosa differ in the production of an ecologically important class of proteinaceous toxins known as bacteriocins, and how overall competitive ability depends on the production of and resistance to these bacteriocins. We determined bacteriocin gene content in a diverse collection of environmental and CF isolates and measured bacteriocin-mediated inhibition, resistance and the outcome of competition in a shared environment between all possible pairs of these isolates at 25°C and 37°C. Although CF isolates encoded significantly more bacteriocin genes, our phenotypic assays suggest that they have diminished bacteriocin-mediated killing and resistance capabilities relative to environmental isolates, regardless of incubation temperature. Notably, however, although bacteriocin killing and resistance profiles significantly predicted head-to-head competitive outcomes, CF and environmental isolates did not differ significantly in their competitive ability. This suggests that the contribution of bacteriocins to competitive ability involves selection on other traits that may be pleiotropically linked to interference competition mediated by bacteriocins.

Generalized Growth of Estuarine, Household and Clinical Isolates of Pseudomonas aeruginosa

Pseudomonas aeruginosa is an opportunistic pathogen of particular concern to immune-compromised people, such as cystic fibrosis patients and burn victims. These bacteria grow in built environments including hospitals and households, and in natural environments such as rivers and estuaries. However, there is conflicting evidence whether recent environments like the human lung and open ocean affect P. aeruginosa growth performance in alternate environments. We hypothesized that bacteria recently isolated from dissimilar habitats should grow differently in media containing artificial versus natural resources. To test this idea, we examined growth of P. aeruginosa isolates from three environments (estuary, household, and clinic) in three media types: minimal-glucose lab medium, and media prepared from sugar maple leaves or big bluestem grass. We used automated spectrophotometry to measure high-resolution growth curves for all isolate by media combinations, and studied two fitness parameters: growth rate and maximum population density. Results showed high variability in growth rate among isolates, both overall and in its dependence on assay media, but this variability was not associated with habitat of isolation. In contrast, total growth (change in absorbance over the experiment) differed overall among habitats of isolation, and there were media-specific differences in mean total growth among habitats of isolation, and in among-habitat variability in the media-specific response. This was driven primarily by greater total growth of estuary isolates when compared with those from other habitats of origin, and greater media-specific variability among household isolates than those from other habitats of origin. Taken together, these results suggest that for growth rate P. aeruginosa bacteria appear to be broad generalists without regard to current or recent habitat, whereas for total growth a signature of recent ecological history can be detected.