Search

Permafrost soils are extreme environments that exert low-temperature, desiccation, and starvation stress on bacteria over thousands to millions of years. To understand how Psychrobacter arcticus 273-4 survived for >20,000 years in permafrost, transcriptome analysis was performed during growth at 22[degrees]C, 17[degrees]C, 0[degrees]C, and -6[degrees]C using a mixed-effects analysis of variance model. Genes for transcription, translation, energy production, and most biosynthetic pathways were downregulated at low temperatures. Evidence of isozyme exchange was detected over temperature for D-alanyl-D-alanine carboxypeptidases (dac1 and dac2), DEAD-box RNA helicases (csdA and Psyc_0943), and energy-efficient substrate incorporation pathways for ammonium and acetate. Specific functions were compensated by upregulation of genes at low temperature, including genes for the biosynthesis of proline, tryptophan, and methionine. RNases and peptidases were generally upregulated at low temperatures. Changes in energy metabolism, amino acid metabolism, and RNase gene expression were consistent with induction of a resource efficiency response. In contrast to results observed for other psychrophiles and mesophiles, only clpB and hsp33 were upregulated at low temperature, and there was no upregulation of other chaperones and peptidyl-prolyl isomerases, relA, csdA, and dac2 knockout mutants grew more slowly at low temperature, but a dac1 mutant grew more slowly at 17[degrees]C. The combined data suggest that the basal biological machinery, including translation, transcription, and energy metabolism, is well adapted to function across the growth range of P. arcticus from -6[degrees]C to 22[degrees]C, and temperature compensation by gene expression was employed to address specific challenges to low-temperature growth.

High-quality habitats for wildlife (e.g., forest) provide essential ecosystem services while increasing species diversity and habitat connectivity. Unfortunately, the presence of such habitats adjacent to produce fields may increase risk for contamination of fruits and vegetables by enteric bacteria, including Escherichia coli. E. coli survives in extrahost environments (e.g., soil) and could be dispersed across landscapes by wildlife. Understanding how terrestrial landscapes impact the distribution of soil E. coli strains is of importance in assessing the contamination risk of agricultural products. Here, using multilocus sequence typing, we characterized 938 E. coli soil isolates collected from two watersheds with different landscape patterns in New York State, USA, and compared the distribution of E. coli and the influence that environmental selection and dispersal have on the distribution between these two watersheds. Results showed that for the watershed with widespread produce fields, sparse forests, and limited interaction between the two land use types, E. coli composition was significantly different between produce field sites and forest sites; this distribution appears to be shaped by relatively strong environmental selection, likely from soil phosphorus, and slight dispersal limitation. For the watershed with more forested areas and stronger interaction between produce field sites and forest sites, E. coli composition between these two land use types was relatively homogeneous; this distribution appeared to be a consequence of wildlife-driven dispersal, inferred by competing models. Collectively, our results suggest that terrestrial landscape attributes could impact the biogeographic pattern of enteric bacteria by adjusting the importance of environmental selection and dispersal. IMPORTANCE Understanding the ecology of enteric bacteria in extrahost environments is important for the development and implementation of strategies to minimize preharvest contamination of produce with enteric pathogens. Our findings suggest that watershed landscape is an important factor influencing the importance of ecological drivers and dispersal patterns of E. coli. Agricultural areas in such watersheds may have a higher risk of produce contamination due to fewer environmental constraints and higher potential of dispersal of enteric bacteria between locations. Thus, there is a perceived trade-off between priorities of environmental conservation and public health in on-farm food safety, with limited ecological data supporting or refuting the role of wildlife in dispersing pathogens under normal operating conditions. By combining field sampling and spatial modeling, we explored ecological principles underlying the biogeographic pattern of enteric bacteria at the regional level, which can benefit agricultural, environmental, and public health scientists who aim to reduce the risk of food contamination by enteric bacteria while minimizing negative impacts on wildlife habitats. [ABSTRACT FROM AUTHOR]

Physiologic and genomic methods are employed to study the micro-organisms such as psychrobacter arcticus isolated from subzero environments. The results suggested that increased protein flexibility due to amino acids that promoted structural instabilities are major adaptation employed by P. arcticus to maintain activity at low temperatures.

Escherichia coli is continuously dispersed into diverse non-host environments and this process may lead to the selection for biodiversity in its genome. Previous work has demonstrated that a small set of E. coli isolates from soil exhibit enhanced biofilm motility. Further work demonstrated that these phenotypes were enhanced, compared to E. coli K-12, at soil relevant temperatures of 15 and 22[degrees]C. To test theories about the role of the soil environment in E. coli biodiversity, we isolated a collection of 322 E. coli from phylogroup D, the most genetically diverse of E. coli subspecies. We asked, 'What is the diversity of motility phenotypes in these isolates?' The environmental Escherichia coli isolates taken from soil samples were tested for their motility. We assessed their motility in swim plates. 15 were found to be non-motile, 72 slightly motile, and the remaining 235 isolates were motile or very motile. The isolates that proved to be non-motile were screened by PCR to determine the size of their flhD operons. The flhD operon encodes the flagellar master regulator FlhD/FlhC. Insertion sequence elements in the operon can eliminate motility. None of the 15 non-motiles showed an increase in size of their flhD operon. The isolates were then tested for mutations in the flhD operon with complementation analysis, using a plasmid that expressed both FlhD and FlhC to see if motility could be restored. Motility has been complemented in two of eight isolates tested., Collin Pirner * (U), Shelley Horne, Birgit Pruess, and Peter Bergholz Department of Microbiological Sciences, North Dakota State University Support: Support: The work was funded by Research and Creative Activates [...]

Technological advancements, particularly in the field of geographic information systems (GIS), have made it possible to predict the likelihood of foodborne pathogen contamination in produce production environments using geospatial models. Yet, few studies have examined the validity and robustness of such models. This study was performed to test and refine the rules associated with a previously developed geospatial model that predicts the prevalence of Listeria monocytogenes in produce farms in New York State (NYS). Produce fields for each of four enrolled produce farms were categorized into areas of high or low predicted L. monocytogenes prevalence using rules based on a field's available water storage (AWS) and its proximity to water, impervious cover, and pastures. Drag swabs (n = 1,056) were collected from plots assigned to each risk category. Logistic regression, which tested the ability of each rule to accurately predict the prevalence of L. monocytogenes, validated the rules based on water and pasture. Samples collected near water (odds ratio [OR], 3.0) and pasture (OR, 2.9) showed a significantly increased likelihood of L. monocytogenes isolation compared to that for samples collected far from water and pasture. Generalized linear mixed models identified additional land cover factors associated with an increased likelihood of L. monocytogenes isolation, such as proximity to wetlands. These findings validated a subset of previously developed rules that predict L. monocytogenes prevalence in produce production environments. This suggests that GIS and geospatial models can be used to accurately predict L. monocytogenes prevalence on farms and can be used prospectively to minimize the risk of preharvest contamination of produce., (Copyright © 2016, American Society for Microbiology. All Rights Reserved.)