Description

Salmonella is a gram-negative bacteria, meaning it has an outer membrane along the cell wall along with proteins as well.



The bacteria is rod-shaped, but since it is gram-negative it is not part of the bacilli grouping.

The bacteria has many flagella around it.

There are over 2500 types of salmonella strains known to man.

Reproduction

Salmonella reproduce by binary fission. This is an asexual way to reproduce, and only produces two, generally identical cells from the original one. This reproductions occurs at a rapid rate, producing once every 20-40 minutes if the conditions are prime. The new cells then follow the lytic cell cycle to continue reproducing.

Keeping salmonella in a cooler place inhibits growth, but doesn't kill the bacteria. Storing chicken in the fridge won't let the bacteria grow, but the chicken will still have salmonella.

Salmonella spreads very quickly through infected animals, since infected chickens can pass salmonella bacteria on to their eggs. Even touching salmonella carrying foods or surfaces can get you infected.

Gas Exchange

Salmonella bacteria is a single celled organism and is constantly in contact with the external environment it lives in. This means the gas exchange occurs through diffusion between the membranes of the salmonella bacteria and host cell. The diffusion in a movement of molecules from a high concentration to a place where the molecules are in low concentration. Since the salmonella bacteria is close to the host cells the gas exchange occurs easily.

Life Cycle

The salmonella bacteria has an interesting life cycle. In order to reproduce or even survive the bacteria needs to have a host, as only certain strains can live for semi-long periods outside a host body. Once the bacteria have entered the body, either through eating contaminated foods or touching infected feces, the bacteria begin to grow.

Some animals that carry salmonella for long periods of time are either resistant to the bacteria or just long-term hosts. Animal and bird feces have salmonella bacteria in them even after the bacteria is no longer active inside them.

The bacteria invades the walls on the intestinal track, thus causing inflammation and damage to the body, causing a variety of symptoms. The liver and spleen have a higher concentration of salmonella while the blood, heart, kidneys, gallbladder, and pancreas have much lower concentrations. The gallbladder, however, is the main site a carriage. If left untreated or serious the infection can spread through the bloodstream to other organs, joints, placenta or fetus, and membranes around the brain. The toxic substances released by the bacteria can effect the rest of the body, as well, damaging it even further.

Habitat

Salmonella can live in a variety of habitats. Some strains of salmonella live in water, soil, food plants, and feces of contaminated humans. Salmonella is present in chicken and chicken produce, unpasteurized milk, ground meat, and fish, as well. Generally the bacteria is able to access those places through cross contamination of already infected organisms or feces. When present in water, salmonella can live for several weeks; in soil the bacteria can live up to several years, while in feces the bacteria may only survive a few days. The bacteria can survive in salt water and cooler environments, but a too hot of an environment may kill the bacteria. This is why cooking food thoroughly can prevent salmonella poisoning.

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Treatment and Prevention

Salmonella can go untreated without harm to humans unless the human infected in very young or elderly; the bacteria has entered the bloodstream; or is a stronger strain of salmonella, such as typhoid. If the salmonella needs treatment the use of antibiotics is common. However, due to the use of antibiotics in animal produce, certain strains of salmonella are immune to most antibiotics and may require stronger medicine and further treatment.

Preventing salmonella is easy. People can only catch salmonella by eating contaminated foods, drinking contaminated water, or coming into contact of feces of infected hosts. There are many ways to prevent contact with salmonella bacteria. Thoroughly cook meats, since the animal may have come into contact with salmonella. This also means not to cross contaminated foods, like cutting raw chicken and using the same knife to cut foods that won’t be cooked. Make sure the blood, juices, and any other forms of contact from raw meat and meat products (eggs and unpasteurized milk) will not come into contact with foods that will not be cooked or anything that will come into contact with your mouth. Also, if you come into contact with both animal and human feces remember proper hygiene and to wash your hands to remove the salmonella bacteria.

Biodiversity and Survival

The relationship between the salmonella bacteria and human or animal host is called parasitism symbiosis. Parasitism symbiosis is when one species benefits from the relationship while the other suffers. The salmonella bacteria benefits while inside the host body and the host suffers and may even die because of it. The salmonella bacteria is known as an endoparasite. This is because as the salmonella bacteria lives inside the host body, not outside.

The biodiversity of the salmonella bacteria helps the bacteria survive. This is because different strains of salmonella effect living things differently. Certain strains of salmonella bacteria only effect certain species and certain hosts. One strain of salmonella only effects animals and won’t harm humans. This helps them survive because some hosts cannot fight back or are more susceptible to salmonella than others. Other strains have different symptoms when the host gets infected, ranging from severe to minor. This allows the bacteria to stay in the body longer before going noticed. Other strains also have a different strength of infection, meaning it could be harder for them to get killed and easier for them to survive in the body. One example of this is known as typhoid fever, which is caused by a strain of salmonella. Typhoid fever usually causes death if left untreated. Some strains of salmonella live in different environments, giving them a larger range of infection and helps them survive. Another way diversity has helped salmonella survive is the fact that some strains of salmonella can live outside the body longer, meaning the have a better chance of infecting others and lasting longer.