Proteobacteria

PROTEOBACTERIA

Proteobacteria are a phylum or subset of gram-negative bacteria. These can be found everywhere. There are five classifications of these bacteria, called alphaproteobacteria, betaprotobacteria, gammaproteobacteria, deltaproteobacteria, and epsilonproteobacteria.

The alpha-proteobacteria are what are called oligotrophs. These are organisms that can live in environments that are very low in nutrients. They live deeply underground, deep in the ocean, or within glacial ice. Chlamydia and Rickettsia are alpha-proteobacteria that are obligate intracellular pathogens. They are inactive when not within a cell because they cannot make ATP energy by themselves. Rickettsia species can cause Rocky Mountain spotted fever, which is transmitted through infected tick bites. Another species causes epidemic typhus, while still another causes endemic typhus.

Chlamydia is another type of alpha-proteobacteria. These are also obligate intracellular pathogens. They are spread via inactive elementary bodies, which are like endospores to become activated within an epithelial cell. Chlamydia trachomatis will be the causative agent in a common sexually-transmitted disease. There are other alpha-proteobacteria that are also obligate intracellular pathogens.

The class called beta-proteobacteria are different from the alpha-proteobacteria because they require a great deal of nutrients in order to grow. They grow between aerobic and anaerobic areas of the human intestine and some are pathogenic to humans. Neisseria gonorrhoeae is one of these that causes the sexually-transmitted disease called gonorrhea. Another species will cause certain types of bacterial meningitis. They do not tolerate a great deal of oxygen and form pairs called diplococci. Bordetella pertussis causes whooping cough and is also difficult to grow in culture.

Organisms that are gamma-proteobacteria are diverse and can cause human diseases. Pseudomonas is one of these. It can infect burns and wounds and can be seen in people who are immunosuppressed. Antibiotic resistance is common with these organisms. Pasteurella is another type of these organisms. These are passed from animal bites to humans. Haemophilus species also cause human diseases, including respiratory