A Microbial Biorealm page on the genus Streptococcus agalactiae
Higher order taxa
cellular organisms; Bacteria; Firmicutes; Bacilli; Lactobacillales; Streptococcaceae; Streptococcus
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.
Streptococcus agalactiae, often referred as Group B Streptococcus (GBS) is a gram-positive streptococcus and originally discovered as a cause of bovine mastitis. GBS is part of the normal bacterial flora colonizing the gastrointestinal(GI) tract and genitourinary tract of a significant proportion of the human population. However, it occasionally become a infectious pathogen colonizing the uterus, blood, brain, and meninges. This pathogen is one of the leading causes of invasive infections in non-pregnant immunocompromised individuals and also causes bacteremia, septicaemia, meningitis, and pneumonia. Colonization of the rectum and vagina of pregnant women with GBS is correlated with GBS sepsis in newborn infants with early onset disease. Streptococcus agalactiae usually appears in the form of long chains and can be isolated in infected site of human or in secretions from infected mammary gland of female cattle and related ungulates. In some samples these are numerous and easily found in stained films; in other cases the organisms may be so scarce that they can be located only with great difficulty. Also, most stains can be used to stain GBS to locate them, since the GBS is gram-positive and readily stained. Streptococcus agalactiae poses a serious threat to lives of neonates, responsible for 2-3 cases per 1000 live birth and to lives of human, especially elderly persons and those with weakened immune systems. This microorganism is considered one of the major causes of economic losses to dairy producers without a control program. Because of its significance as an threat to both human and related ungulates, such as cow, its genome was sequenced and still being studied to gain more insight into the virulence factor and to develop treatments and preventive prophylactic antibodies.
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 or ganism's lifestyle?
WORK IN PROGRESS
The genome of eight strains in Streptococcus agalactiae (GBS) have been completely sequenced: Streptococcus agalactiae 18RS21, Streptococcus agalactiae 2603V/R, Streptococcus agalactiae 515, Streptococcus agalactiae A909, Streptococcus agalactiae CJB111, Streptococcus agalactiae COH1, Streptococcus agalactiae H36B, Streptococcus agalactiae NEM316.
Streptococcus agalactiae NEM316 is the serotype III strain isolated from urine of a fatal case of septicaemia. Serotype is the subclassification of this species and serotype III is causing significant percentage of both early and late onset diseases.
Complete genome sequence of this strain is a circular dsDNA chromosome with 2,211,285 nt (GC content of 35%, coding content of 87%) and contains 2235 genes, 2082 protein coding genes, 101 structural RNSs, and 36 pseudogenes. Genome sequence was completed in 2002/11/15.
Analysis of NEM316 genome predicted and identify locus responsible for extracellular products like capsular polysaccharide, surface proteins, and secreted proteins, which are involved in virulence and contributing to pathogenesis. Strain contains 17 genes (cpsA-L, neuBCDA) along with the transcriptional gene cpsY for sialyated capsular polysacchraide, 30 genes (gbs 0391, 0392, 0393, and 27 more genes) for surface proteins containing cell wall, and various genes responsible for 71 secreted proteins.
In strain NEM315, it was observed that there are 12 genes encoding proteins related to plasmid functions, which are replication, partition or transfer, and genes were found in the vicinity of integrase genes.
Streptococcus agalactiae contains two completely sequenced plasmids, pGB 354 and pGB3631. pGB 354 is a circular DNA plasmid with 6,437 nt (GC content of 32% and coding content of 62%) and contains 5 genes, 5 protein coding genes, no structural and pseudo genes. Genome sequence was completed 1997/03/04. pGB 3631 is also a circular DNA plasmid with 5,842 nt (GC content of 33% and coding content of 62%) and contains 9 genes, 6 protein coding genes, no structural and pseudo genes, and 4 other genes. Genome sequence was completed 1994/07/13.
In genomic analysis of NEM315, it was revealed to have stress adaption by encoding Clp proteins (gbs 1634, 1383, 1869, 1367, 0535), which is ATP-dependent protease playing a role in virulence. Also, the genome was analyzed to have several chromosal islands, which is unique feature different from other streptococcus, but rather similar to pathogenic Escherichia coli . This unexpected similarity built hypothesis that virulence factor was on the unique chromosomal island for both species and evolve them into pathogens. But this hypothesis was not yet tested.
Cell structure and metabolism
Describe any interesting features and/or cell structures; how it gains energy; what important molecules it produces.
carbon? hetero auto? energy -CHEKC
Cellular Features: Streptococcus agalactiae is a non-acid fast Gram-positive baterium (cell wall?? exaplain?). This species is non-motile, catalase (an enzyme that catalyzes the reduction of hydrogen peroxide) - free diplococcal (a pair of cocci, circular, pair) (~2.0 µm) that occur in pairs or short chains. It also does not form spores and often known as Group B Streptococcus due to the presence of group B Lancefield antigen. This species is also B-hemolytic (determined base on hemolysis on blood agar plates). virulence factor - surface protein. - genes or pseudogenes epxressing surface prtotein to adhere to mucosal surfacs and evade host defense.
Environment: Streptococcus agalactiae is host-associated facultative anaerobe, (generation of ATP?explain). The optimal temperature for this species is at 37 Celcius degree (mesophile).
Glucose Oxidation: Oxidative phosphorylation: able to synthesize ATP by oxidative phosphorulation. structural genoes for cytochrome bd quinol oxidase (high affinity for oxygen and a low energetic yield) and NADH dehydrogenase. enzymes contributing to aerobic growth of this species. no gene involved in heme synthesis --> could use external source of heme, but no corresponding transporter detected.
able to ferment different carbon sources to multiple by-products, lactate, acetate, ethanol, formate or acetoin
worth noting that bioenergetic mecahnism of this more related to L. lactis than other pathogenic streptococci - seen in genes coding for bd oxidase and some feremnt pathwyas have ortholog (explain) only in gene seq. of L alctise .
capacity to import a broad range of carbon souces 17 sugar-specific phosphoenolpyruvate-dependent phosphotransferase system (PTS) enyzme II complex identified. specificity including cellobioise, beta-glucoside, trehalose, mannose, lactose, fructose, mannitol, N-acetylgalactosamine, and glucose.
4 sugar-specific ABC transporter, 3 glycerol permeases and one glycerol-phosphate permease. 68% similiar to that of Shigella flexneri - horizonal gene tranfer between two enteric bacteria.
enezymes necessary glycolysis all present and that pentose phosphate pathway is only involved in pentose and gluconate utilization but not by-pass glysolysis (penotose-phosphate cycle_. --> broad catabolic capacity, may reflect its ability to adapt to various env.
require a great number of AA for grwoth. missing TCA cycle - depriving from ability to synthesize the precursors of most AA. only biosynthetic pathwyas for Ala, Ser, Gly, Glutamine, asparatate, asparagine, and threonine - present
addition of proline not required although missing genes.
auxotropic for most AA. needs to importe compoounds from exogenous sources. support by 8 ABC transporter and permease specific for AA.
another source - degradation of peptides by peptidase 4 genes encoding exported peptidase, 3 ABC transporters specific for oligopeptides, 21 genes for intracellular peptidase (some known to play a role in virulence)
high number of transporters related to AA
but also a broad tranport capacity 255 genes most abundant class ABC tranposete
no complete vitamin biosyntheic some permease? with not yet unknown fxn.
a larger set of transporters for different inorganic componds, like two phosphate and two iron ABC tranporters and several cation tranport systmes.
diverse -->? surive and multiply in diff env and cause disease.
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.
S. agalactiae is a pathogen which is the leading cuase of invasice infections in neonates and causes septicaemia, meningitis and pneumonia (in adults, osteomyelitis, septic arthritis, postpartum sepsis, amnionitis, urinary tract infection, and still birth. )
S. agalactiae expresses a variety of extracellular products, implicated in vriulence. These includes the capsular polysacchardie, surface proteins and secreted protein. Two distinct polysaccharide antigens of the sialylated capsular polysaccharide, one of the most important S. agalactiae virulence factors, are possessed. This inhibits deposition of the host complement factor C3b and thus, complement-mediated opsonophagocytosis. Surface proteins plays an crucial rile during the infectious process by mediating interactions between the pahigen and the host cells and/or evasion for the host defense. The polysaccharide antiphagocytic capsule is this bacterium's main virulence factor.
"Associated with diseases of the newborn; 90% of cases have septicemia, 40% have pulmonary involvement, and 30% have meningeal involvement; early onset disease acquired in utero or during passage through the birth canal and can have a case fatality rate of 50%; late onset disease with onset from 1 week to 3 months after birth have a case fatality rate of 20% and are probably acquired from the environment: survivors of meningitis cases can be left with hearing loss, blindness, cerebral palsy, mental retardation and/or epilepsy; adult infections include pneumonia, urinary tract infection, peritonitis, meningitis, endocarditis, osteomyelitis and rarely pharyngitis"
Application to Biotechnology
Does this organism produce any useful compounds or enzymes? What are they and how are they used?
bMouse Anti-Streptococcus agalactiae Monoclonal Antibody, Unconjugated, Clone 424
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.]
[www.cdc.gov/ncidod/eid/vol10no8/pdfs/03-0917.pdf John F. Bohnsack,* April A. Whiting,* Gabriela Martinez,† Nicola Jones,‡ Elisabeth E. Adderson,§ Shauna Detrick,* Anne J. Blaschke-Bonkowsky,* Naiel Bisharat,‡ and Marcelo Gottschalk† " Serotype III Streptococcus agalactiaefrom Bovine Milk and Human Neonatal Infections".Emerging Infectious Diseases • Vol. 10, No. 8, August 2004]
Edited by Ha Bean Kim,student of Rachel Larsen and Kit Pogliano