Dual Expression of the Salmonella Effector SrfJ in Mammalian Cells and Plants

Salmonella Type III Secretion Effector SrfJ: A Glucosylceramidase Affecting the Lipidome and the Transcriptome of Mammalian Host Cells

Type III secretion systems are found in many Gram-negative pathogens and symbionts of animals and plants. Salmonella enterica has two type III secretion systems associated with virulence, one involved in the invasion of host cells and another involved in maintaining an appropriate intracellular niche. SrfJ is an effector of the second type III secretion system. In this study, we explored the biochemical function of SrfJ and the consequences for mammalian host cells of the expression of this S. enterica effector. Our experiments suggest that SrfJ is a glucosylceramidase that alters the lipidome and the transcriptome of host cells, both when expressed alone in epithelial cells and when translocated into macrophages in the context of Salmonella infection. We were able to identify seventeen lipids with higher levels and six lipids with lower levels in the presence of SrfJ. Analysis of the forty-five genes, the expression of which is significantly altered by SrfJ with a fold-change threshold of two, suggests that this effector may be involved in protecting Salmonella from host immune defenses.

Identification of Salmonella carriers by amplification of FimA, Stn and InvA genes and bacterial culture methods in fecal samples of buffalo

Salmonellosis is one of the most important bacterial diseases in human and animals. Rapid diagnosis and sub sequence accurate treatment of Salmonella carriers help reduce the salmonellosis in human and livestock animals. In this study, 420 fecal samples were taken during year 2019 from buffalo in the Urmia, Khoy and Piranshahr regions in west Azerbaijan province, Iran. Samplings were carried out in different seasons. Presence of Salmonella invasion genes (FimA, Stn and InvA) were evaluated by polymerase chain reaction. The bacterial culture and biochemical tests were performed on feces samples for isolation of bacterium Salmonella; however, all samples were negative in culture method. PCR findings showed that, 50 (11.90%) fecal samples were positive to the genes. The analysis of results showed that frequency of salmonellosis outbreak in different parts of west Azerbaijan province followed a similar pattern and the incidence of salmonellosis according to forecast in the warm seasons (spring and summer) was more than in cold seasons (autumn and winter). The prevalence of Salmonella in buffalo's feces based on warm and cold seasons were 32 (64.00%) and 18 (36.00%), respectively. The results showed significant difference between cold and warm season in the prevalence of salmonellosis. Therefore, the application of molecular technics is essential for the prevention and treatment of salmonellosis. The results also showed that specificity of PCR method was better than culture method for detection of Salmonella in feces sample.

Synergistic Effects of Limosilactobacillus fermentum ASBT-2 with Oxyresveratrol Isolated from Coconut Shell Waste

Value-added phytochemicals from food by-products and waste materials have gained much interest and among them, dietary polyphenolic compounds with potential biological properties extend a promising sustainable approach. Oxyresveratrol (Oxy), a stilbenoid polyphenol, possesses great therapeutic potential, though its pharmacokinetic issues need attention. A good source of oxyresveratrol was found in underutilized coconut shells and the synbiotic applications of the compound in combination with a potential probiotic isolate Limosilactobacillus fermentum ASBT-2 was investigated. The compound showed lower inhibitory effects on the strain with minimum inhibitory concentration (MIC) of 1000 µg/mL. Oxyresveratrol at sub-MIC concentrations (500 µg/mL and 250 µg/mL) enhanced the probiotic properties without exerting any inhibitory effects on the strain. The combination at sub- MIC concentration of the compound inhibited Salmonella enterica and in silico approaches were employed to elucidate the possible mode of action of oxy on the pathogen. Thus, the combination could target pathogens in the gut without exerting negative impacts on growth of beneficial strains. This approach could be a novel perspective to address the poor pharmacokinetic properties of the compound.

Novel molecular components involved in callose-mediated Arabidopsis defense against Salmonella enterica and Escherichia coli O157:H7

BACKGROUND

Food contamination with Salmonella enterica and enterohemorrhagic Escherichia coli is among the leading causes of foodborne illnesses worldwide and crop plants are associated with > 50% of the disease outbreaks. However, the mechanisms underlying the interaction of these human pathogens with plants remain elusive. In this study, we have explored plant resistance mechanisms against these enterobacteria and the plant pathogen Pseudomonas syringae pv. tomato (Pst) DC3118, as an opportunity to improve food safety.

RESULTS

We found that S. enterica serovar Typhimurium (STm) transcriptionally modulates stress responses in Arabidopsis leaves, including induction of two hallmark processes of plant defense: ROS burst and cell wall modifications. Analyses of plants with a mutation in the potentially STm-induced gene EXO70H4 revealed that its encoded protein is required for stomatal defense against STm and E. coli O157:H7, but not against Pst DC3118. In the apoplast however, EXO70H4 is required for defense against STm and Pst DC3118, but not against E. coli O157:H7. Moreover, EXO70H4 is required for callose deposition, but had no function in ROS burst, triggered by all three bacteria. The salicylic acid (SA) signaling and biosynthesis proteins NPR1 and ICS1, respectively, were involved in stomatal and apoplastic defense, as well as callose deposition, against human and plant pathogens.

CONCLUSIONS

The results show that EXO70H4 is involved in stomatal and apoplastic defenses in Arabidopsis and suggest that EXO70H4-mediated defense play a distinct role in guard cells and leaf mesophyll cells in a bacteria-dependent manner. Nonetheless, EXO70H4 contributes to callose deposition in response to both human and plant pathogens. NPR1 and ICS1, two proteins involved in the SA signaling pathway, are important to inhibit leaf internalization and apoplastic persistence of enterobacteria and proliferation of phytopathogens. These findings highlight the existence of unique and shared plant genetic components to fight off diverse bacterial pathogens providing specific targets for the prevention of foodborne diseases.