Streptococcus pneumoniae
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Classification
Higher order taxa
Domain: Bacteria
Phylum: Firmicutes
Class: Diplococci
Order: Lactobacillales
Family: Streptococcaceae
Genus: Streptococcus
Species
Species: S. pneumoniae
Description and significance
Streptococcus pneumoniae, also called pneumococcus, is a gram-positive, pathogenic bacterium capable of causing numerous infections. It the most common cause of pneumonia and bacterial meningitis, and is commonly found in the upper respiratory tract of humans. S. pneumoniae is shaped like a lancet, a type of knife with a short wide two-edged blade. It is alpha hemolytic (a classification method using the breakdown of red blood cells) and is usually between 0.5 and 1.25 micrometers in size.
S. pneumoniae was first isolated in 1881 simultaneously by U.S. Army physician George Sternberg and French chemist Louis Pasteur. In 1928 by Frederick Griffith and 1944 by Avery, MacLeod and McCarty, S. pneumoniae was used to prove that genetic material consists of DNA.
Genome structure
S. pneumoniae has a 2,160,837 base pair genome sequence. Its chromosome is circular and has 2236 coding regions. Approximately 5% of the genome is composed of insertion sequences that may contribute to genome rearrangements through uptake of foreign DNA. S. pneumoniae has shown a significant increase in antibiotic resistance over the past few decades, due to its rapid growth rate and genetic rearrangements.
Cell structure and metabolism
S. pneumoniae is completely surrounded by a capsule made up of polysaccharides. The capsule interferes with phagocytosis by preventing opsonization of its cells. The cell wall of S. pneumoniae is six layers thick and made up of peptidoglycan with teichoic and lipoteichoic acids. Within these acids are choline-binding proteins (CBPs), which adhere to choline receptors on human cells. S. pneumoniae has pili, which are hair-like structures extending from its surface. It also has more than 500 surface proteins, including five penicillin binding proteins (PBPs), two neuraminidases, an IgA protease, as well as choline-binding proteins as stated previously.
S. pneumoniae gains a substantial amount of carbon and nitrogen using extracellular enzyme systems which allow for the metabolism of polysaccharides and hexosamines. These systems also damage host tissues and facilitate colonization.
Ecology
S. pneumoniae is commonly found in the upper respiratory tract of humans, specifically the nasopharynx region. It is found in 5-10% of healthy adults, and 20-40% of healthy children. S. pneumoniae is non-pathogenic unless it travels outside the normal inhabited region, where it will then become pathogenic and cause different infections depending on the area in which it makes it way into.
S. pneumoniae sometimes shares its normal habitat with the pathogen Haemophilus influenzae. Individually each pathogen thrives on its own. However, when both pathogens inhabit the region at the same time, after 2 weeks only H. influenzae survives. Immune response caused by H. influenzae leads to the death of S. pneumoniae.
Pathology
How does this organism cause disease? Human, animal, plant hosts? Virulence factors, as well as patient symptoms.
Application to Biotechnology
Does this organism produce any useful compounds or enzymes? What are they and how are they used?
Current Research
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References