About Mycoplasmas
Mycoplasma bacteria are often referred as the "fried egg" bacteria because of the culture appearance on agar. These bacteria have the simplest structure needed to sustain life. Mycoplasma bacteria are unique in the prokaryotic world since they are the only genus with no cell wall. They also have one of the smallest genomes consisting of only 500 to 1000 genes. It's believed this unique bacterium evolved from gram positive bacteria, mainly from the genus Clostridia.
Pathogenesis
Mycoplasma are a species of bacterium that infect and proliferate in the respiratory and urogenital tract of the host. Mycoplasma pneumoniae is one of the main causes of the infection most commonly known as pneumonia. This bacterium attaches to the epithelium tissue of the lungs and excrete hydrogen peroxide and superoxide radicals. These radicals cause tissue damage in the lungs. However, the main contributors to disease symptoms are the immune factors sent to fight off the infection. The induction of cytokines and macrophages help exacerbate many of the pneumonia symptoms.
Structure
The typical shape of a Mycoplasma colony is coccus (round clusters). It's also one of the smallest bacterium genuses with the smallest diameter measuring 300 nanometers. Another unique characteristic about this bacteria is that they multiple through a process called binary fission. The composition of a Mycomplasma colony is two thirds protein and one third lipids.
Molecular Biology
The molecular structure of mycoplasma bacteria is the typical genome of a circular, double-stranded DNA molecule. Because of the small amount of genes represented in this genus, mycoplasma bacteria also have few of the proteins and enzymatic reactions that other bacteria contain. An interesting aspect of mycoplasma is its viral similarities since it depends on the host for many of the nutrients necessary for replication.
Host Response
The initial host response for infection is the existence of antibodies. The first antibodies to respond are the IgM class, but subsequently the IgA class is detected. However, both of these classes are important in host defenses. Scientists have identified that host defenses play a large role in pathogenesis of the bacteria.
Epidemiology
The most susceptible patients of mycoplasma bacteria are children under the age of four. Adults are also susceptible, but children under the age of six months are less likely to contract the disease, suggesting immunity passed by the mother. Mycoplasma is responsible for 15 to 20 percent of pneumonia cases in the population. Incubation periods are between two to three weeks; it is spread by respiratory droplets from person to person.
