Streptococcus sanguinis

Classification

Higher order taxa

Eubacteria; Firmicutes; Bacilli; Lactobacillales; Streptococcaceae

Genus species

Streptococcus, S. sanguinis

Description and Significance

Streptococcus sanguinis is a Gram-positive bacteria that lives in human mouth. S. sanguinis is mostly found in dental plaque, which then colonize dental cavities. It is often found in bloodstream where it inhabit in the heart valves and has a key role of causing bacterial endocarditis, which can be a serious heart disease."Fibrin and platelets are deposited at the site of endothelial cell trauma, forming a sterile vegetation where bacteria may adhere and colonize during bacteremia."

Also known as: Streptococcus sanguis

Genome Structure

The genome of Streptococcus sanguinis was determined via whole-gene shotgun sequencing and observed that it has a circular structure of DNA that is consist of 2,388,435 bp. The size of the sequence is significantly larger than the genome of other members of Streptococcus sequenced. S. sanguinis has relatively higher percentage (43.4%) of Guanine and Cytosine base pairing than that of others which requires higher energy to break the Hydrogen bond during the process of replication; it allows to differentiate this organism from other streptococci The genome of this bacteria can encode 2,274 proteins, 61 tRNAs, and four rRNA operons(Xu et al. 2007). It's genome can also encode a sigma factor 70, known as "housekeeping" sigma factor which transcribe genes in a growing cell to keep them alive. "Genome Sequence"

Cell Structure and Metabolism

This organism has a very well-built system for energy production despite an incomplete TCA cycle(Kreb Cycle or Citric acid cycle). It contains many enzymes that enhances metabolic pathways including biosynthesis, pentose phosphate pathway, gluconeogenesis, fermentation of sugars and carbohydrates, and so on. Such enzymes used for gluconeogenesis allows the bacterium to convert amino acids into fructose-6-phosphate, an important metabolic precursor used to make peptidoglycan(cell wall) and an initial substrate required for pentose phosphate pathway. Many of these enzymes were found in other streptococci and some are not present.

Pathology

S. sanguinis directly binds to oral surfaces and serves as a tether for the attachment of a variety of other oral microorganisms which colonize the tooth surface, form dental plaque, and contribute to the etiology of both caries and periodontal disease(Xu et al. 2007).

Current Studies

Studies were done to understand the relationship between S. sanguinis and other oral bacteria such as mutans streptococci. Specifically, study was done to analyze colonization of bacterium,its proportion, and the role of saliva during formation of dental plaque within mother-infant pairs. Study concluded that the tooth emergence increases as the proportion of saliva in mouth increases. Also, they discovered that S. sanguinis and mutans streptococci have an inverse relationship that when mutans streptococci colonize tooth, less S. sanguinis is present. Results suggest different ways of controlling dental caries.