Streptococcus agalactiae

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A Microbial Biorealm page on the genus Streptococcus agalactiae


Higher order taxa

cellular organisms; Bacteria; Firmicutes; Bacilli; Lactobacillales; Streptococcaceae; Streptococcus


NCBI: Taxonomy

Streptococcus agalactiae

Description and significance

Describe the appearance, habitat, etc. of the organism, and why it is important enough to have its genome sequenced. Describe how and where it was isolated. Include a picture or two (with sources) if you can find them.

S. agalactiae, also referred to as group B streptococci (GBS) is a commensal bacterium colonizing the intestinal track of a significant proportion of the human population.

Genome structure

Describe the size and content of the genome. How many chromosomes? Circular or linear? Other interesting features? What is known about its sequence? Does it have any plasmids? Are they important to the organism's lifestyle?

The genome is 2 211 485 bases pairs long and contains 2118 protein coding genes.

Strains within S. agalactiae:

The genome of S. agalactiae strain NEM316, responsible for a fatal case of septicaemia, consists of a circular chromosome of 2 211 485 base pairs (bp). G+C content of genome is 35.6%, which is significantly lower than that of the genomes of S. pyogenes (38.5%) and of S. pneumoniae (39.7%). Seven sets of ribosomal RNA (23S, 5S and 16S) were identified to be organized within a 450kb region located on the right replichore of the chromosome next to the origin of replication (figure). 80 tRNA genes are identified, which recognize 31 out of 61 possible sense codons. The genome of strain NEM316 contains 2082 protein coding genes with 36 pseudogens. the gene orientation was observed to be strongly biased, as 81% of the coding sequences (CDS) are transcribed in the same orientation as the movement of the replication fork. This characteristic bias of gene orientation appears to be common feature of low G+C Gram positive bacteria.

Cell structure and metabolism

Describe any interesting features and/or cell structures; how it gains energy; what important molecules it produces.


Describe any interactions with other organisms (included eukaryotes), contributions to the environment, effect on environment, etc.


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

Enter summaries of the most recent research here--at least three required


Philippe Glaser, Christophe Rusniok, Carmen Buchrieser, Fabien Chevalier, Lionel Frangeul, Tarek Msadek, Mohamed Zouine, Elisabeth Couvé, Lila Lalioui, Claire Poyart, Patrick Trieu-Cuot, Frank Kunst "Genome sequence of Streptococcus agalactiae, a pathogen causing invasive neonatal disease".Molecular Microbiology. 2002. 45 (6), 1499–1513.doi:10.1046/j.1365-2958.2002.03126.x

[Ferretti, J.J., McShan, W.M., Ajdic, D., Savic, D.J., Savic, G.,Ferretti, J.J., McShan, W.M., Ajdic, D., Savic, D.J., Savic, G., M1 strain of Streptococcus pyogenes. Proc Natl Acad Sci USA 98: 4658–4663.]

[Tettelin, H., Nelson, K.E., Paulsen, I.T., Eisen, J.A., Read, T.D., Peterson, S., et al. (2001) Complete genome sequence of a virulent isolate of Streptococcus pneumoniae. Science 293: 498–506.]

Edited by Ha Bean Kim,student of Rachel Larsen and Kit Pogliano