Campylobacter jejuni transcriptome changes during loss of culturability in water

Abstract

BackgroundWater serves as a potential reservoir for Campylobacter, the leading cause of bacterial gastroenteritis in humans. However, little is understood about the mechanisms underlying variations in survival characteristics between different strains of C. jejuni in natural environments, including water.ResultsWe identified three Campylobacter jejuni strains that exhibited variability in their ability to retain culturability after suspension in tap water at two different temperatures (4°C and 25°C). Of the three, strains C. jejuni M1 exhibited the most rapid loss of culturability whilst retaining viability. Using RNAseq transcriptomics, we characterised C. jejuni M1 gene expression in response to suspension in water by analyzing bacterial suspensions recovered immediately after introduction into water (Time 0), and from two sampling time/temperature combinations where considerable loss of culturability was evident, namely (i) after 24 h at 25°C, and (ii) after 72 h at 4°C. Transcript data were compared with a culture-grown control. Some gene expression characteristics were shared amongst the three populations recovered from water, with more genes being up-regulated than down. Many of the up-regulated genes were identified in the Time 0 sample, whereas the majority of down-regulated genes occurred in the 25°C (24 h) sample.ConclusionsVariations in expression were found amongst genes associated with oxygen tolerance, starvation and osmotic stress. However, we also found upregulation of flagellar assembly genes, accompanied by down-regulation of genes involved in chemotaxis. Our data also suggested a switch from secretion via the sec system to via the tat system, and that the quorum sensing gene luxS may be implicated in the survival of strain M1 in water. Variations in gene expression also occurred in accessory genome regions. Our data suggest that despite the loss of culturability, C. jejuni M1 remains viable and adapts via specific changes in gene expression.

Strain-Specific Differences in Survival of Campylobacter spp. in Naturally Contaminated Turkey Feces and Water

“…The low temperature (4°C) employed in the current study was intentionally chosen to enhance the potential to detect differences in survival among different strains of C. jejuni and C. coli shed by the birds in the feces. Campylobacter strains can differ in their cold tolerance (41)(42)(43)(44), and such differences may contribute to the current findings. In addition to temperature, other attributes, including the avian source (chicken versus turkey) and the Campylobacter species and strains involved, may contribute to the observed differences in survival between our study and others.…”

Detection and Quantification of Viable but Non-culturable Campylobacter jejuni

“…However, C. jejuni lacks these typical osmotic protective systems that are common in other Gram-negative bacteria (Garenaux et al, 2008;Cameron et al, 2012). Instead, several genes have been implicated in responding to hyperosmotic conditions in C. jejuni, including htrB (encoding high-temperature response protein B), ppk (encoding polyphosphate kinase), a sensor histidine kinase (CJM1_1208) (Bronowski et al, 2017), and gltD and glnA that encode proteins for glutamate and glutamine synthesis, respectively (Cameron et al, 2012). Further study is required to determine if these genes are actively transcribed and play potential roles in the progression of C. jejuni into the VBNC state under osmotic stress or not.…”

Characterization of Swedish Campylobacter coli clade 2 and clade 3 water isolates

“…Most water survival studies for Campylobacter have been performed using C. jejuni isolates and survival times have ranged from 2 weeks to 4 months (Cools et al, 2003;Rollins & Colwell, 1986;Trigui et al, 2015). In several studies, autoclaved tap water has been used to obtain sample reproducibility and to avoid influence of native water microbiota (Bronowski et al, 2017;Buswell et al, 1998). Here, the short-term survival of all the Swedish C. coli water isolates was analyzed in autoclaved tap water.…”

“…Studies on different C. jejuni isolates have shown that the survival time in water at a low temperature varies between 2 weeks and 4 months (Cools et al, 2003;Rollins & Colwell, 1986;Trigui, Thibodeau, Fravalo, Letellier, & Faucher, 2015). It has also been noted that C. jejuni isolates derived from various sources exhibit different water survival potential (Bronowski et al, 2017;Buswell et al, 1998;Cools et al, 2003;Jones, Sutcliffe, & Curry, 1991). These differences have been suggested to be a consequence of variation in the genetic content between the isolates (Trigui et al, 2015).…”