Listeria Analysis monocytogenes Transcriptomic Response to Bile in Aerobic and Anaerobic Conditions
Listeria Analysis is a foodborne sickness caused by Listeria Analysis monocytogenes, a gram-positive facultative anaerobic bacteria. The pathogenicity of this bacterium depends on its ability to survive in anaerobic, acidic and bile environments present throughout the gastrointestinal (GI) tract.
The goal of this transcriptomics study was to look at the changes in transcript levels created under GI tract-like circumstances. RNA obtained from L. monocytogenes strain F2365 was used to examine changes in transcript levels in both aerobic and anaerobic settings after exposure to 0 and 1 per cent bile at acidic and neutral pH.
Under the conditions tested, transcripts corresponding to genes involved in disease, cell wall-related proteins, DNA repair,
transcription factors, and stress responses had varying amounts. Internals, listeriolysin O, and other virulence factors, as well as many histidine sensory kinases, all had different transcript levels after being exposed to anaerobiosis in acidic conditions.
These results suggest that the anaerobiosis response affects the transcription of several genes involved in L. monocyte gene survival in acidic and bile environments in different ways. Although more research is needed to determine the role of oxygen in the pathogenesis of L. monocytogenes, these findings provide valuable insight into how this pathogen interacts with the GI tract.
Listeria Analysis: A Quick Overview
Listeriosis is caused by the Gram-positive pathogen Salmonella analysis monocytogenes, which is found in food (Scallan et al., 2011). Listeriosis is more likely to affect pregnant women, infants, the elderly, and immunocompromised people, with symptoms including meningitis, septicemia, and spontaneous miscarriages (Thigpen et al., 2011). As a foodborne pathogen, this bacterium must be able to cope with stressors that arise after consuming contaminated food. Low pH, bile, and hypoxic/anoxic conditions are only a few of the major stresses that L.monocytogenes in the gastrointestinal (GI) tract (Davis et al., 1996). One of the first stresses experienced by L. monocytogenes in the following intake is a low stomach pH.
(White et al., 2015). The low pH of the stomach discharge acts as a barrier against bacterial invasion. The SOS response, LisRK (a two-component regulatory system governing listerial osmotolerance), components of the sigma B regulon, proton ATPasepump, and the enzyme systems that regulate
the internal concentration of hydrogen ions are all involved in the acid response of Listeria (Sleator and Hill, 2005).
The transcript levels of sigma B and prefer controlled genes, such as internals, phospholipases, and other virulence genes, increased in Listeria cultured in
the presence of organic acids, according to transcriptome analysis. Oxidative stress defences, DNA repair, intermediate metabolism, cell wall modification, and cofactor and fatty acid biosynthesis were all up-regulated in this earlier study (Tessema et al., 2012).
Proteome analysis of Listeria cultured in the presence of organic salts revealed that oxidoreductases and lipoproteins were up-regulated. Proteins involved in respiration (enzyme dehydrogenases and reductases), osmolyte transport, protein folding and repair,
general stress resistance, flagella formation, and metabolism were all expressed in response to hydrochloric acid exposure (Bowman et al., 2012).
Survival of Listeria Analysis monocytogenes in Gastrointestinal Tract Models
Under anaerobic conditions, Listeria monocytogenes grow at a significantly slower rate (Figures 1A vs. 1B). Under anaerobic conditions, bile had a varied effect on the viability of L. monocytogenes strain F2365. Bile had no effect on the survival of L. monocytogenes strain F2365 in aerobic (Figure 1A)
or anaerobic (Figure 1B) conditions at neutral pH. (Figure 1B).
The percentage of L. monocytogenes that survived at an acidic pH in the presence of bile, which replicates bile exposure in the duodenum, decreased dramatically (Figure 2A; p 0.05). This depicts how bile’s toxicity rises when it is exposed to acidic circumstances. Under anaerobic conditions, survival similarly decreased as compared to time 0 h (Figure 2B, p 0.05). In comparison to aerobic conditions (Figure 2A; p 0.05), the loss in viability was less severe in anaerobic conditions (Figure 2B). This suggests that anaerobic circumstances help L. monocytogenes survive the harmful effects of bile.
Overall Changes in Transcript Levels in Response to Gastrointestinal Tract-Mimicking Conditions
Because significant changes in survival were detected after 1 hour of bile exposure under acidic circumstances, this time point was chosen to compare
the effect of oxygen on the transcriptome. The overall alterations in transcripts observed are shown in Table 1. In comparison to aerobic settings, 190 transcripts in media at pH 7.5 and 268 transcripts in the medium at pH 5.5 were shown to be differentially expressed under anaerobic conditions. At pH 7.5 and 5.5, 304 and 434 transcripts were differentially
generated in the presence of bile and in the absence of oxygen, respectively. Variations in the transcript levels of 200 genes were detected in anaerobic conditions when exposed to bile at pH 7.5 and 419 at pH 5.5. Except for acidic bile conditions during anaerobic development,
there were more transcripts identified as up-regulated than down-regulated in all circumstances evaluated.
The Effects of Anaerobic Conditions on Transcript Levels\Listeria Analysis
Under anaerobic conditions, transcripts from five genes were found to have higher expression levels, regardless of whether the cultivation was done at a neutral or acidic pH. (Table 2 and Supplementary Figure 1). Genes involved in membrane transport, protein folding, and stress response were among them. In comparison to acidic pH, the amino acid transporter (LMOf2365 2333) had roughly a 9-fold rise in levels at neutral pH.
Under anaerobic conditions at both pH levels studied, transcripts representing the dnaJ (LMOf2365 1491) and dnaK (LMOf2365 1492) genes, which
encode for molecular chaperones and have roles in phagocytosis and protein homeostasis, were similarly enhanced. Under oxygen-deficient conditions, the mRNA for the cadA (LMOf2365 0672) gene, which encodes for a heavy metal translocating P-type ATPase and is a component of the Cadac efflux cassette, rose 6.1-fold at pH 7.5 and 3.8-fold at pH 5.5. (Table 2).
Regardless of the pH state examined, transcript levels of 18 genes were reduced under anaerobic conditions (Table 3 and Supplementary Figure 2). Six of the eighteen transcripts were uncharacterized
putative proteins, and all of them showed lower transcript levels under neutral conditions than under acidic ones. This could imply that these hypothesised genes are controlled in the same way. Stress response, membrane-associated protein, and metabolic protein were among the remaining transcripts discovered (Table 3).
Transcript Levels in Anaerobic Acidic Environments
140 genes’ transcript levels increased in acidic conditions (Table 4 and Supplementary Figure 1), while 104 genes’ transcrip
levels decreased in anaerobic conditions(Table 4 and Supplementary Figure 1). (Table 5). The survival of L. monocytogenes was influenced by several biological pathways related to pathogenesis, stress response, membrane-associated proteins, transcription factors, and DNA repair mechanisms, according to an analysis of these
up-regulated transcripts in response to acidic conditions under anaerobiosis (Table 4). Genes involved in metabolism, transcription factors, and pathogenesis all had transcripts that were down-regulated (Table 5). Under acidic anaerobic circumstances, the number of transcripts encoding glycolytic enzymes also increased (Table 4). The phosphoglycerate mutase (4.7-fold increase), glyceraldehyde-3-phosphate dehydrogenase (5.4-fold increase), and pyruvate kinase (5.4-fold increase) were among them (6.7-fold increase).
Under anaerobic conditions, changes in transcript levels in response to bile
In response to exposure to bile in anaerobic circumstances, transcripts representing 53 genes were found to be up-regulated (Table 6 and Supplementary Figure 3). Transcripts encoding transcription regulators of virulence, antibiotic resistance, metabolism, and membrane related proteins all increased in expression (Table 6). Under anaerobic circumstances in the presence of bile at both pH 7.5 and 5.5, transcripts representing nine genes were down-regulated (Table 7 and Supplementary Figure 4). Genes involved in metabolism, translation, pathogenesis, and transcription had their transcript levels reduced by a factor of two (Table 7).
Under Acidic and Anaerobic Conditions, Changes in Transcript Levels in Response to Bile
Under anaerobic conditions, acidic pH bile upregulated transcription levels of 210 genes (Table 8 and Supplementary Figure 3). Upregulation has also been found in transcripts encoding transcription factors, metabolism, replication and repair, cell signalling, protein folding, and disease. Additionally, under anaerobic conditions with acidic bile, transcripts representing 146 genes were
down-regulated (Table 9 and Supplementary Figure 4), with the majority of these genes
being involved in metabolism, membrane transport, replication and repair, pathogenesis, and transcription factors.