Salmonella Typhimurium BRD509

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Classification

cellular organisms; Bacteria; Proteobacteria; Gammaproteobacteria; Enterobacteriales; Enterobacteriaceae [1]

Genus Species

Salmonella enterica; subsp. enterica serovar Typhimurium, strain BRD509 [1]

Colonies of pathogenic bacteria growing on an agar culture plate - Salmonella enterica (serovar typhimurium)

Description and Significance

Give a brief description of the microorganism and explain why you think it is important. How does it relate to the other organisms in its phylum (bacteria and fungi) or group (archaea, virus, protist). Use the following for each reference in text (change number accordingly)--> [1]

Salmonella Typhimurium, along with all bacteria of the genus Salmonella, are gram-negative, rod-shaped (bacillus), and facultatively anaerobic bacteria that are within the family Enterobacteriaceae. Salmonella Typhimurium is an important subspecies of Salmonella as when it is used within a mouse model the pathogenesis and symptoms of infection mimic those of a human infection with Salmonella Typhi (the causative agent of typhoid fever). Using a mouse model and Salmonella Typhimurium allows researchers to look for antigens that are conserved across various subspecies and look for antigens that could possibly be vaccine candidates. The strain BRD509 is of great importance in the mouse model and also in this search for possible vaccine candidates as it is an attenuated strain that retains many of the antigenic components that trigger an adaptive immune response allowing for infection to occur without killing the host. This allows for options such as challenge with a virulent strain of salmonella, sacrificing mice and specific time points and viewing the cell populations using flow cytometry based methods as well as other things.

Structure, Metabolism, and Life Cycle

Interesting features of its structure; how it gains energy (how it replicates, if virus); what important molecules it produces (if any), does it have an interesting life cycle?

Ecology and Pathogenesis

Salmonella Typhimurium, much like all other species of the genus Salmonella, naturally live within the gastrointestinal system of both animals and humans. More specifically Salmonella thrives within the intestinal tract as it is not made to withstand the high acidity of the stomach.

The pathogenesis of Salmonella is begins when contact with contaminated food or water occurs. Contamination occurs through contact of fecal matter with the food or water source and can occur through a lack of proper hygiene of an infected individual or it is also possible for insects, primarily flys, to play a role in contamination as they move from contaminated fecal matter to a food source.[2] After entering into the host and making passing into the intestinal tract the bacteria will colonize the intestines, and then work to enter dendritic cells, enterocytes and M cells (microfold cells) along the intestinal epithelium. This process of entering into the host cells makes use of a series of a type III secretion system (T3SS1 as well as having many PAMPS (pathogen associated molecular patterns) the the host cell will detect and attempt to phagocytosis the Salmonella. However, the Salmonella creates a barrier preventing it from being broken down called the Salmonella containing vacuole, allowing the Salmonella to be carried to lymph tissues such as the lymph nodes as well as the spleen. Some of the other virulence factors that play a role in pathogenesis are another type III secretion system (T3SS2) which plays a role in virulence as well as survival within macrophages, two genes on a virulence plasmid spvB and spvC both of which play unique roles in hindering the host defenses, superoxide dismutase which protects Salmonella by neutralizing reactive oxygen species that are produced by the host and a variety of ion acquisition proteins that collect required ions for cellular replication and bring them back to the Salmonella. [3] After infection occurs the patient suffering salmonellosis would experience gastroenteritis the symptoms of which will generally include nausea, vomiting, diarrhea that will sometimes include with blood and mucus, and slight fever. The salmonellosis will generally pass within a few days, after which the individual may obtain some degree of immunity, in infants less then one year old bloodstream infection (sepsis) is common and thus antibiotic treatment is recommended. If extreme cases of diarrhea and vomiting are experienced it might be necessary for someone suffering salmonellosis to enter the hospital to receive IV liquids to prevent dehydration from reaching a dangerous level. [2]


[2] = Britanica [3] = Salmonella the ultimate...

References

[1] EXAMPLE ONLY. REPLACE WITH YOUR REFERENCES. Takai, K., Sugai, A., Itoh, T., and Horikoshi, K. 2000. "Palaeococcus ferrophilus gen. nov., sp. nov., a barophilic, hyperthermophilic archaeon from a deep-sea hydrothermal vent chimney". International Journal of Systematic and Evolutionary Microbiology. 50: 489-500. http://ijs.sgmjournals.org/cgi/reprint/50/2/489

Author

Page authored by Joshua McCarra, student of Mandy Brosnahan, Instructor at the University of Minnesota-Twin Cities, MICB 3301/3303: Biology of Microorganisms.