Abstract
Toxigenic Vibrio cholerae, ubiquitous in aquatic environments, is responsible for cholera; humans can become infected after consuming food and/or water contaminated with the bacterium. The underlying basis of persistence of V. cholerae in the aquatic environment remains poorly understood despite decades of research. We recently described a “persister” phenotype of V. cholerae that survived in nutrient-poor “filter sterilized” lake water (FSLW) in excess of 700-days. Previous reports suggest that microorganisms can assume a growth advantage in stationary phase (GASP) phenotype in response to long-term survival during stationary phase of growth. Here we report a V. cholerae GASP phenotype (GASP-700D) that appeared to result from 700 day-old persister cells stored in glycerol broth at −80°C. The GASP-700D, compared to its wild-type N16961, was defective in motility, produced increased biofilm that was independent of vps (p<0.005) and resistant to oxidative stress when grown specifically in FSLW (p<0.005). We propose that V. cholerae GASP-700D represents cell populations that may better fit and adapt to stressful survival conditions while serving as a critical link in the cycle of cholera transmission.
Highlights
Cholera is a major public health threat worldwide, in countries where safe drinking water, adequate sanitation and hygiene are suboptimal [1]
To ensure that growth advantage in stationary phase (GASP)-700D was viable at the inoculation site, we examined a block of agar consisting of the entire inoculation site as described in methods section
Because V. cholerae motility and the polar flagellum contribute to biofilm formation [19,29], we were interested in determining the role(s) of the novel bipolar and possible non-productive/deleted peritrichous flagella elicited by N16961S-24 and GASP-700D, respectively, in biofilm formation when grown in nutrient-poor filter sterilized’’ lake water (FSLW)
Summary
Cholera is a major public health threat worldwide, in countries where safe drinking water, adequate sanitation and hygiene are suboptimal [1]. The role(s) of rugose variant of V. cholerae in epidemic cholera is limited because not all V. cholerae strains are capable of switching to rugose variant even in a medium promoting high-frequency rugose production [9] Amid this conundrum, we recently reported that a subset of culturable V. cholerae assume what we have termed a ‘‘persister’’ phenotype in a ‘‘filter sterilized’’ lake water (FSLW) microcosm model [11]. As we were not certain if 700 day-old persister cells of microcosm origin will retain their genetic and phenotypic traits unchanged upon storage in glycerol broth, for our convenience, we refer this glycerol-stored cells to GASP-700D phenotype; in contrast, wild-type V. cholerae N16961S strain grown overnight statically in FSLW at room temperature will be termed as N16961S-24 (Table). We provide evidence that GASP-700D showed no motility in soft agar; produced biofilm only in nutrientpoor FSLW; and conferred resistance to oxidative stress when compared to N16961S-24
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