What are examples of two helpful Bacteria and two harmful Bacteria?

Examples of helpful bacteria:

Lactobacillus Bacteria: There are several different species of this type of bacteria. These include: Lactobacillus acidophilus, Lactobacillus reuteri, and Lactobacillus planatarum. They are gram-positive, rod shaped bacteria. Lactobacillus bacteria are beneficial in several ways:

• They make up parts of the normal human oral, intestinal, and vaginal flora. 


• They are able to ferment lactose to lactic acid. This makes them important as a preservative and in yogurt production.

Streptomyces Bacteria: There are several different species of this type of bacteria. These include: Streptomyces aureofaciens, Streptomyces rimosus, and Streptomyces griseus. They are gram-positive, filamentous bacteria. Streptomyces bacteria are beneficial in the following ways:

• They are important in the decomposition of organic substances in soil.


• Some species are used in the production of antibacterial and antifungal substances.

Examples of harmful bacteria: 

Helicobacter pylori: These bacteria colonize the lining of the stomach. They are gram-negative rod shaped bacteria. H. pylori bacteria cause stomach ulcers by producing ammonia and cytotoxins which damage the lining of the stomach.

Clostridium tetani: These bacteria enter the body through wounds. They are gram-negative rod shaped bacteria. These bacteria produce the disease tetanus. Tetanus causes muscle spasms and death from respiratory failure.