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Transcriptomic response of Listeria monocytogenes during the transition to the long-term-survival phase.

ABSTRACT: Listeria monocytogenes can change its cellular morphology from bacilli to cocci during the transition to the long-term-survival (LTS) phase. The LTS cells demonstrated increased baro- and thermotolerance compared to their vegetative counterparts. So far, the underlying mechanisms that trigger this morphological and physiological transition remain largely unknown. In this study, we compared the transcriptomic profiles of L. monocytogenes serotype 4b strain F2365 at different growth stages in tryptic soy broth with yeast extract (TSBYE) using a whole-genome DNA chip approach. We identified a total of 225 differentially expressed genes (?4-fold; P < 0.05) during the transition to the LTS phase in TSBYE. Genes related to cell envelope structure, energy metabolism, and transport were most significantly upregulated in the LTS phase. The upregulation of compatible solute transporters may lead to the accumulation of cellular solutes, lowering intracellular water activity and thus increasing bacterial stress resistance during the transition to the LTS phase. The downregulation of genes associated with protein synthesis may indicate a status of metabolic dormancy of the LTS cells. The transcriptomic profiles of resuscitated LTS cells in fresh TSBYE resembled those of log-phase cells (r=0.94), as the LTS cells rapidly resume metabolic activities and transit back to log phase with decreased baro- and thermotolerance.

SUBMITTER: Wen J

PROVIDER: S-EPMC3165388 | biostudies-literature | 2011 Sep

REPOSITORIES: biostudies-literature

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Transcriptomic response of Listeria monocytogenes during the transition to the long-term-survival phase.

Wen Jia J Deng Xiangyu X Li Zengxin Z Dudley Edward G EG Anantheswaran Ramaswamy C RC Knabel Stephen J SJ Zhang Wei W

Applied and environmental microbiology 20110715 17

Listeria monocytogenes can change its cellular morphology from bacilli to cocci during the transition to the long-term-survival (LTS) phase. The LTS cells demonstrated increased baro- and thermotolerance compared to their vegetative counterparts. So far, the underlying mechanisms that trigger this morphological and physiological transition remain largely unknown. In this study, we compared the transcriptomic profiles of L. monocytogenes serotype 4b strain F2365 at different growth stages in tryp ...[more]

PMID: 21764970

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Project description:The foodborne pathogen Listeria monocytogenes survives exposure to a variety of stresses including desiccation in the food industry. Strand-specific RNA sequencing was applied to analyze changes in the transcriptomes of two strains of L. monocytogenes (Lm 568 and Lm 08-5578) during desiccation [15°C, 43% relative humidity (RH)] on food grade stainless steel surfaces over 48 h to simulate a weekend with no food production. Both strains showed similar survival during desiccation with a 1.8-2 Log CFU/cm2 reduction after 48 h. Analysis of differentially expressed (DE) genes (>twofold, adjusted p-value <0.05) revealed that the initial response to desiccation was established after 6 h and remained constant with few new genes being DE after 12, 24, and 48 h. A core of 81 up- and 73 down-regulated DE genes were identified as a shared, strain independent response to desiccation. Among common upregulated genes were energy and oxidative stress related genes e.g., qoxABCD (cytochrome aa3) pdhABC (pyruvate dehydrogenase complex) and mntABCH (manganese transporter). Common downregulated genes related to anaerobic growth, proteolysis and the two component systems lmo1172/lmo1173 and cheA/cheY, which are involved in cold growth and flagellin production, respectively. Both strains upregulated additional genes involved in combatting oxidative stress and reactive oxygen species (ROS), including sod (superoxide dismutase), kat (catalase), tpx (thiol peroxidase) and several thioredoxins including trxAB, lmo2390 and lmo2830. Osmotic stress related genes were also upregulated in both strains, including gbuABC (glycine betaine transporter) and several chaperones clpC, cspA, and groE. Significant strain differences were also detected with the food outbreak strain Lm 08-5578 differentially expressing 1.9 × more genes (726) compared to Lm 568 (410). Unique to Lm 08-5578 was a significant upregulation of the expression of the alternative transcription factor σB and its regulon. A number of long antisense transcripts (lasRNA) were upregulated during desiccation including anti0605, anti0936, anti1846, and anti0777, with the latter controlling flagellum biosynthesis and possibly the downregulation of motility genes observed in both strains. This exploration of the transcriptomes of desiccated L. monocytogenes provides further understanding of how this bacterium encounters and survives the stress faced when exposed to dry conditions in the food industry.

Project description:The foodborne bacterium Listeria monocytogenes (Lm) causes a range of diseases, from mild gastroenteritis to invasive infections that have high fatality rate in vulnerable individuals. Understanding the population genomic structure of invasive Lm is critical to informing public health interventions and infection control policies that will be most effective especially in local and regional communities. We sequenced the whole draft genomes of 936 Lm isolates from human clinical samples obtained in a two-decade active surveillance program across 58 counties in New York State, USA. Samples came mostly from blood and cerebrospinal fluid. We characterized the phylogenetic relationships, population structure, antimicrobial resistance genes, virulence genes, and mobile genetic elements. The population is genetically heterogenous, consisting of lineages I-IV, 89 clonal complexes, 200 sequence types, and six known serogroups. In addition to intrinsic antimicrobial resistance genes (fosX, lin, norB, and sul), other resistance genes tetM, tetS, ermG, msrD, and mefA were sparsely distributed in the population. Within each lineage, we identified clusters of isolates with ≤ 20 single nucleotide polymorphisms in the core genome alignment. These clusters may represent isolates that share a most recent common ancestor, e.g., they are derived from the same contamination source or demonstrate evidence of transmission or outbreak. We identified 38 epidemiologically linked clusters of isolates, confirming eight previously reported disease outbreaks and the discovery of cryptic outbreaks and undetected chains of transmission, even in the rarely reported Lm lineage III (ST3171). The presence of animal-associated lineages III and IV may suggest a possible spillover of animal-restricted strains to humans. Many transmissible clones persisted over several years and traversed distant sites across the state. Our findings revealed the bacterial determinants of invasive listeriosis, driven mainly by the diversity of locally circulating lineages, intrinsic and mobile antimicrobial resistance and virulence genes, and persistence across geographical and temporal scales. Our findings will inform public health efforts to reduce the burden of invasive listeriosis, including the design of food safety measures, source traceback, and outbreak detection.

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Transcriptomic response of Listeria monocytogenes during the transition to the long-term-survival phase.

Publications

Transcriptomic response of Listeria monocytogenes during the transition to the long-term-survival phase.

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