Free Example of Microbiology Essay

Salmonella enterica is a gram negative rod shaped non-spore forming enterobacteria. It is a flagellate motile bacterium of a diameter ranging between 0.7 to 15 µm, with a length of 2 to 5 µm. Since they are chemo-organisms, they get their energy through reduction and oxidation of reactions with the use of organic sources.

The naming of Salmonella species initially was in respect to clinical considerations, e.g. Salmonella enterica (enteritis). After scientists discovered that many species’ host specificities were non-existing, the latest strains received naming depending on the location of isolation (Neidhardt & Curtiss, 1996). The facultative anaerobes exude hydrogen sulfide, which can easily be detected when grown in a ferrous sulfate containing media such as TSI. A good number of isolates exists in two phases: non-motile phase II and motile phase I.

Salmonella enterica is a zoonotic disease-causing microorganism that can be transferred between animals and humans. Majority of the infections resulting from Salmonella enterica is due to ingestion of food containing contaminates. A distinction between Salmonella typhoid/paratyphoid and Salmonella enteritis is that the later has a capsule protein and an extraordinary virulence factor that can cause severe infection. They enter the cells through macropinosomes, and this means that they are intracellular pathogens of facultative nature (Neidhardt & Curtiss, 1996).           

Enteric salmonella consists of almost all serotypes of the Salmonella bacterium, with the majority of them were never found in humans. These organisms enter the host through the digestive tract. In order to cause infection they must be in large numbers. The gastric acid destroys majority of the bacteria that enter the body. Infants are the most susceptible to infection since a small quantity of Salmonella enterica ingestion can result in the disease. Salmonella causes inflammation of the intestines with muco-purulent and bloody diarrhea. Dehydration caused by excessive diarrhea leads to the heavy water losses and can results in severe toxicosis with mild symptoms (Neidhardt & Curtiss, 1996).

Outside a living cell, Salmonella enterica can still survive for weeks because it is not affected by freezing temperatures. Their demise can be accelerated by heat and ultraviolet radiation. Bacteria are killed at a temperature of 131°F (55 °C) during a period of ninety minutes or at 140 °F (60 °C) during twelve minutes.

Lactococcus lactis (Nonpathogenic Organism)

Lactococcus lactis (formerly Streptococcus lactis) is a non-pathogenic gram-positive bacterium, which is used in the milk industry for extensive production of cheese and milk butter. It recently became popular as the first organism to undergo genetic modification and is used alive for successful treatment of human diseases (Saeed, 1999). Lactococcus lactis is grouped as coccus that congregates in short chains and pairs depending on the prevailing growth conditions. They are non-motile bacteria that do not produce spores. The bacterium is characterized by homofermentative metabolism that produces lactic acid in extremely large quantities. When bacteria are cultured in a low PH medium, scientists report that it can produce D (-) lactic acid. The ability to produce lactic acid has made Lactococcus lactis be regarded as the most vital microorganism in the dairy industry (Saeed, 1999).

Scientist regards it as an opportunistic pathogen. However, in the last decade, a number of clinical cases were associated with these microorganisms in both animals and humans. If added to milk Lactococcus lactis uses enzymes to produce ATP molecules from lactose in anaerobic conditions. Lactic acid is the byproduct of ATP energy. The milk containing bacteria curdles because of the lactic acid produced, and when the curds are separated, they can be used in the production of cheese (Saeed, 1999).

Discussions were always caused by the issue of using of Lactococcus. lactis in factories. Lactococcus lactis specific bacteriophages result to substantial economic losses annually. They prevent milk substrate from being metabolized fully (Saeed, 1999).This has been supported by numerous researches, which have shown phages responsible for this: c2, 936, and p335 serotypes.