Streptococcus pneumoniae: Meningitis

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Scanning Electron Micrograph of Streptococcus pneumonmiae by R. Facklam, J. Carr, Source: CDC.

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Streptococcus pneumoniae is a non-motile, non-spore forming, gram-positive bacteria of the firmicute phylum. S. pneumoniae is also commonly referred to as pneumococcus [1,2]. Streptococcus pneumoniae are in the shape of a slightly pointed coccus. The diameter of each single pneumococcus organism ranges from 0.5 to 1.25 micrometers. S. pneumoniae is found singly and in short chains, but mainly these bacteria are found in pairs (diplococci) [2]. Streptococcus pneumoniae uses fermentation to produce energy via converting glucose into lactic acid. Furthermore, Streptococcus pneumoniae utilizes extracellular enzyme systems in order to obtain carbon and nitrogen, and these processes damage host tissue and permit S. pneumoniae to colonize the host (Todar 2003). Streptococcus pneumoniae and Haemophilus influenzae contribute to the same mucosal microenvironment. Both bacteria are capable of living on their own. But, Lysenko et al. (2005) showed that Haemophilus influenzae swiftly outcompetes Streptococcus pneumoniae when they are in the same environment. Thus, H. influenzae can remove populations of the S. pneumoniae pathogen (Lysenko et al. 2005).

This bacteria exclusively inhabits human beings and are mesophillic, meaning they optimally inhabit areas with temperatures ranging from 30 to 35 degrees Celsius. Streptococcus pneumoniae is most commonly found in the upper respiratory tract, specifically in the nasopharynx (the nasal passages). Most people carry these bacteria in their nasopharynx, and the harboring of S. pneumoniae within a human is called carriage. Even though most people carry these bacteria in their nasopharynx, most of the time S. pneumoniae does not cause disease [1,2].

A polysaccharide capsule encloses the entire S. pneumoniae cell, and this sugar capsule is key to this bacteria’s virulence. There are hundreds of surface proteins on Streptococcus pneumoniae. Choline-binding proteins are an important group of surface proteins expressed by S. pneumoniae, and this group of proteins helps attach the bacteria to human cells (Todar 2003).

Historical Significance

Louis Pasteur was the first person to isolate Streptococcus pneumoniae, although at the time was only known as pneumococcus because it could cause pneumonia in humans. In 1974, this species of bacteria was officially named Streptococcus pneumoniae because it can form chains in liquid.

Streptococcus pneumoniae was a key bacteria in the development of molecular genetics field. Fred Griffith, in 1928, used S. pneumoniae to discover the transformation process in bacteria (Lederberg et al. 2005). In 1944, building off of Griffith’s findings, Avery, MacLeod, and McCarthy demonstrated that DNA and not protein was the genetic material, using the transformative factor in the Streptococcus pneumoniae (Lederberg et al. 2005).


Bacterial infection via S. pneumoniae spreads from person to person by means of respiratory droplets. Transmission typically occurs when a carrier coughs or sneezes within six feet of other potentially infected people. Carriers are normally healthy, however, these carriers have the potential to be a source of infection for others [1].

Section 3

Include some current research in each topic, with at least one figure showing data.

Section 2

Include some current research in each topic, with at least one figure showing data.

Section 3

Include some current research in each topic, with at least one figure showing data.


Overall paper length should be 3,000 words, with at least 3 figures.


[Sample reference] Takai, K., Sugai, A., Itoh, T., and Horikoshi, K. "Palaeococcus ferrophilus gen. nov., sp. nov., a barophilic, hyperthermophilic archaeon from a deep-sea hydrothermal vent chimney". International Journal of Systematic and Evolutionary Microbiology. 2000. Volume 50. p. 489-500.

Edited by student of Joan Slonczewski for BIOL 238 Microbiology, 2011, Kenyon College.