Dataset Information

Regulation of biofilm components in Salmonella enterica serovar Typhimurium by lytic transglycosylases involved in cell wall turnover.

ABSTRACT: In Salmonella enterica serovar Typhimurium, a biofilm mode of growth known as the rdar morphotype is regulated by several networks which sense multiple environmental signals. The transcriptional regulator CsgD is the major target for these regulatory pathways. In this study, we show that two lytic transglycosylases of family I, MltE and MltC, in combination increase CsgD expression and rdar morphotype. MltE and MltC, which share a highly similar transglycosylase SLT domain, work redundantly to regulate CsgD at the transcriptional and posttranscriptional levels. The effect of MltE and MltC on CsgD levels was independent of the known regulatory pathways that sense cell envelope stress. These findings reveal, for the first time, a specific function of lytic transglycosylases in S. Typhimurium and suggest the existence of a new signaling pathway that links cell wall turnover to biofilm formation.

SUBMITTER: Monteiro C

PROVIDER: S-EPMC3232906 | biostudies-other | 2011 Dec

REPOSITORIES: biostudies-other

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Regulation of biofilm components in Salmonella enterica serovar Typhimurium by lytic transglycosylases involved in cell wall turnover.

Monteiro Claudia C Fang Xin X Ahmad Irfan I Gomelsky Mark M Römling Ute U

Journal of bacteriology 20110930 23

In Salmonella enterica serovar Typhimurium, a biofilm mode of growth known as the rdar morphotype is regulated by several networks which sense multiple environmental signals. The transcriptional regulator CsgD is the major target for these regulatory pathways. In this study, we show that two lytic transglycosylases of family I, MltE and MltC, in combination increase CsgD expression and rdar morphotype. MltE and MltC, which share a highly similar transglycosylase SLT domain, work redundantly to r ...[more]

PMID: 21965572

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Project description:Phage-based biocontrol of bacteria is considered a natural approach to combat foodborne pathogens. Salmonella spp. are notifiable and highly prevalent pathogens that cause foodborne diseases worldwide. In this study, six bacteriophages were isolated and further characterized that infect food-derived Salmonella isolates from different meat sources. The siphovirus VB_StyS-LmqsSP1, which was isolated from a cow's nasal swab, was further subjected to in-depth characterization. Phage-host interaction investigations in liquid medium showed that vB_StyS-LmqsSP1 can suppress the growth of Salmonella species isolates at 37°C for 10 h and significantly reduce the bacterial titer at 4°C. A reduction of 1.4 to 3 log units was observed in investigations with two food-derived Salmonella isolates and one reference strain under cooling conditions using multiplicities of infection (MOIs) of 104 and 105. Phage application on chicken skin resulted in a reduction of about 2 log units in the tested Salmonella isolates from the first 3 h throughout a 1-week experiment at cooling temperature and with an MOI of 105. The one-step growth curve analysis using vB_StyS-LmqsSP1 demonstrated a 60-min latent period and a burst size of 50 to 61 PFU/infected cell for all tested hosts. Furthermore, the genome of the phage was determined to be free from genes causing undesired effects. Based on the phenotypic and genotypic properties, LmqsSP1 was assigned as a promising candidate for biocontrol of Salmonella enterica serovar Typhimurium in food. IMPORTANCE Salmonella enterica is one of the major global causes of foodborne enteritis in humans. The use of chemical sanitizers for reducing bacterial pathogens in the food chain can result in the spread of bacterial resistance. Targeted and clean-label intervention strategies can reduce Salmonella contamination in food. The significance of our research demonstrates the suitability of a bacteriophage (vB_StyS-LmqsSP1) for biocontrol of Salmonella enterica serovar Typhimurium on poultry due to its lytic efficacy under conditions prevalent in food production environments.

Project description:BackgroundTyphoid fever is an acute systemic infection of humans caused by Salmonella enterica subspecies enterica serovar Typhi (S. Typhi). In chronic carriers, the bacteria survive the harsh environment of the gallbladder by producing biofilm. The phenotype of S. Typhi biofilm cells is significantly different from the free-swimming planktonic cells, and studies have shown that they are associated with antibiotic resistance, immune system evasion, and bacterial persistence. However, the mechanism of this transition and the events leading to biofilm formation are unknown. High throughput sequencing was performed to identify the genes involved in biofilm formation and to postulate the mechanism of action.ResultsPlanktonic S. Typhi cells were cultured using standard nutrient broth whereas biofilm cells were cultured in a stressful environment using high shearing-force and bile to mimic the gallbladder. Sequencing libraries were prepared from S. Typhi planktonic cells and mature biofilm cells using the Illumina HiSeq 2500 platform, and the transcriptome data obtained were processed using Cufflinks bioinformatics suite of programs to investigate differential gene expression between the two phenotypes. A total of 35 up-regulated and 29 down-regulated genes were identified. The identities of the differentially expressed genes were confirmed using NCBI BLAST and their functions were analyzed. The results showed that the genes associated with metabolic processes and biofilm regulations were down-regulated while those associated with the membrane matrix and antibiotic resistance were highly up-regulated.ConclusionsIt is proposed that the biofilm phenotype of S. Typhi allows the bacteria to increase production of the membrane matrix in order to serve as a physical shield and to adhere to surfaces, and enter an energy conservation state in response to the stressful environment. Conversely, the planktonic phenotype allows the bacteria to produce flagella and increase metabolic activity to enable the bacteria to migrate and form new colonies of infection. This data provide a basis for further studies to uncover the mechanism of biofilm formation in S. Typhi and to discover novel genes or pathways associated with the development of the typhoid carrier state.

Dataset Information

Regulation of biofilm components in Salmonella enterica serovar Typhimurium by lytic transglycosylases involved in cell wall turnover.

Publications

Regulation of biofilm components in Salmonella enterica serovar Typhimurium by lytic transglycosylases involved in cell wall turnover.

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