Streptococcus dysgalactiae

A Microbial Biorealm page on the genus Streptococcus dysgalactiae

Classification

Higher order taxa

Bacteria; Firmicutes; Bacilli; Lactobacillales; Streptococcaceae; Streptococcus

Species

NCBI: Taxonomy

Streptococcus dysgalactiae

Description and significance

Streptococcus dysgalactiae is a member of group C streptococci (GCS). This gram-positive bacteria is commonly found on the animal and can be isolated found from udders of cows with mild mastitis, an inflammation of the mammalian breast, and from blood and tissues of lambs with polyarthritis, an inflammation of five or more joints. [240 book, S.I.] Although it is extremely rare to be found on human, it can cause meningitis, an inflammation of the protective membrane covering the central nervous system. [2,3]

The virulence factors of group C streptococci were not studied as extensively as much as other streptococci group; as a result, researchers sequenced the whole genome of one strain, NS3396. [8] The study of the sequence revealed a number of similarities between Streptococcus pyogenes, a group A streptococci (GAS), and Streptococcus dysgalactiae. This allows researchers to understand the pathology of Streptococcus dysgalactiae.[8]

Genome structure

The genome of Streptococcus dysgalactiae (strain NS3396) includes a linear chromosome of 38,528 bp and has an average of 37.48% GC content, also known as guanine-cytosine content. [8] This was completed just recently in the year 2007.

Comparative genomic analysis has revealed many significant similarities between the genomes of Streptococcus dysgalactiae and those of group A streptococci (GAS).In addition, a large proportion of the open reading frames (ORFs), 83%, corresponds to hypothetical phage proteins and well- known phage proteins. [8] This reveals that not only Streptococcus dysgalactiae and GAS are closely related, but they are also part of the lactic acid bacteria, bacteria that uses lactic acid metabolism. [9]

While the genomes between both groups have close resemblance, there are four regions on Streptococcus dysgalactiae that shows little or no similarities with GAS. The first region, contains ORF3 to ORF7, which codes the lysogeny module. Researchers concluded that this region shows high levels of nucleotide diversity.[9] The second region contains IRF12 to ORF22, which codes for the whole DNA replication module. It is concluded that there might have been potential modular recombination events.[9] The bacteria might also have a unique methlase. The third region contains ORF45 that codes for ClustralW alignment at protein level. Researchers observed that while the first 639 amino acid are identical between S. dysgalactiae and GAS, the remaining 736 amino acid shows more variation. This suggests that there might have been a level of evolutionary adaptation for the cell wall. [9] The fourth region codes for tail fiber, host lysis, and lysogenic conversion modules, which suggest that S. dysgalactiae might have evolved a number of special proteins for the ability to attach to bacterial surface and lysis. [9]

The genome structures between Streptococcus dysgalactiae and GAS also shows that there are lacteral gene transfer between both groups, which makes the species a remarkable adaptor. [9]

Cell structure and metabolism

Role of Cell Surface Protein

The bacteria contain proteins known as the M protein on their cell surfaces that specifically bind to tissue proteins of the host. It can also resist phagocytosis, which helps resisting against immune cells. [10]

In a study of Streptococcus dysgalactiae, strain 8215, researchers isolated a gene called demA that encode for protein DemA. This protein share many homologous features of M and M-like protein. [10] The significance of this protein is that it can completely inhibit the binding of fg (fibrinogen). Fibrinolytic system is used by human body to control level of inflamation. [15] Therefore, by inhibiting fg, the microbe is capabable of resisting human body immune system. [10]

Further analysis reveals that dmgA, an order reading frame (ORF), is encoded before demA. dmgA codes for the protein DmgA, which exhibits many features of Mga Protein in Streptococcus pyogenes. Both the Mga Protein and DmgA are known to take part of microbe's pathogenesis. [10]

Ecology

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

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

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

References

[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 Rachel Larsen