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Streptococcus is a genus of gram-positive coccus or spherical bacteria that belongs to the family Streptococcaceae, within the order Lactobacillales, in the phylum Bacillota. Cell division in streptococci occurs along a single axis, so as they grow, they tend to form pairs or chains that may appear bent or twisted. This differs from staphylococci, which divide along multiple axes, thereby generating irregular, grape-like clusters of cells. Most streptococci are oxidase-negative and catalase-negative, and many are facultative anaerobes.
Streptococcus pyogenes is a species of Gram-positive, aerotolerant bacteria in the genus Streptococcus. These bacteria are extracellular, and made up of non-motile and non-sporing cocci that tend to link in chains. They are clinically important for humans, as they are an infrequent, but usually pathogenic, part of the skin microbiota that can cause Group A streptococcal infection. S. pyogenes is the predominant species harboring the Lancefield group A antigen, and is often called group A Streptococcus (GAS). However, both Streptococcus dysgalactiae and the Streptococcus anginosus group can possess group A antigen as well. Group A streptococci, when grown on blood agar, typically produce small (2–3 mm) zones of beta-hemolysis, a complete destruction of red blood cells. The name group A (beta-hemolytic) Streptococcus (GABHS) is thus also used.
Streptococcus pneumoniae, or pneumococcus, is a Gram-positive, spherical bacteria, alpha-hemolytic member of the genus Streptococcus. They are usually found in pairs (diplococci) and do not form spores and are non motile. As a significant human pathogenic bacterium S. pneumoniae was recognized as a major cause of pneumonia in the late 19th century, and is the subject of many humoral immunity studies.
The bacterial capsule is a large structure common to many bacteria. It is a polysaccharide layer that lies outside the cell envelope, and is thus deemed part of the outer envelope of a bacterial cell. It is a well-organized layer, not easily washed off, and it can be the cause of various diseases.
Streptococcus mutans is a facultatively anaerobic, gram-positive coccus commonly found in the human oral cavity and is a significant contributor to tooth decay. It is part of the "streptococci", an informal general name for all species in the genus Streptococcus. The microbe was first described by James Kilian Clarke in 1924.
Streptococcus sanguinis, formerly known as Streptococcus sanguis, is a Gram-positive facultative anaerobic coccus species of bacteria and a member of the Viridans Streptococcus group. S. sanguinis is a normal inhabitant of the healthy human mouth where it is particularly found in dental plaque, where it modifies the environment to make it less hospitable for other strains of Streptococcus that cause cavities, such as Streptococcus mutans.
Pathogenomics is a field which uses high-throughput screening technology and bioinformatics to study encoded microbe resistance, as well as virulence factors (VFs), which enable a microorganism to infect a host and possibly cause disease. This includes studying genomes of pathogens which cannot be cultured outside of a host. In the past, researchers and medical professionals found it difficult to study and understand pathogenic traits of infectious organisms. With newer technology, pathogen genomes can be identified and sequenced in a much shorter time and at a lower cost, thus improving the ability to diagnose, treat, and even predict and prevent pathogenic infections and disease. It has also allowed researchers to better understand genome evolution events - gene loss, gain, duplication, rearrangement - and how those events impact pathogen resistance and ability to cause disease. This influx of information has created a need for bioinformatics tools and databases to analyze and make the vast amounts of data accessible to researchers, and it has raised ethical questions about the wisdom of reconstructing previously extinct and deadly pathogens in order to better understand virulence.
Streptococcus sobrinus is a Gram-positive, catalase-negative, non-motile, and anaerobic member of the genus Streptococcus.
Streptococcus iniae is a species of Gram-positive, sphere-shaped bacterium belonging to the genus Streptococcus. Since its isolation from an Amazon freshwater dolphin in the 1970s, S. iniae has emerged as a leading fish pathogen in aquaculture operations worldwide, resulting in over US$100M in annual losses. Since its discovery, S. iniae infections have been reported in at least 27 species of cultured or wild fish from around the world. Freshwater and saltwater fish including tilapia, red drum, hybrid striped bass, and rainbow trout are among those susceptible to infection by S. iniae. Infections in fish manifest as meningoencephalitis, skin lesions, and septicemia.
In the fields of molecular biology and genetics, a pan-genome is the entire set of genes from all strains within a clade. More generally, it is the union of all the genomes of a clade. The pan-genome can be broken down into a "core pangenome" that contains genes present in all individuals, a "shell pangenome" that contains genes present in two or more strains, and a "cloud pangenome" that contains genes only found in a single strain. Some authors also refer to the cloud genome as "accessory genome" containing 'dispensable' genes present in a subset of the strains and strain-specific genes. Note that the use of the term 'dispensable' has been questioned, at least in plant genomes, as accessory genes play "an important role in genome evolution and in the complex interplay between the genome and the environment". The field of study of pangenomes is called pangenomics.
Sortase refers to a group of prokaryotic enzymes that modify surface proteins by recognizing and cleaving a carboxyl-terminal sorting signal. For most substrates of sortase enzymes, the recognition signal consists of the motif LPXTG (Leu-Pro-any-Thr-Gly), then a highly hydrophobic transmembrane sequence, followed by a cluster of basic residues such as arginine. Cleavage occurs between the Thr and Gly, with transient attachment through the Thr residue to the active site Cys residue, followed by transpeptidation that attaches the protein covalently to cell wall components. Sortases occur in almost all Gram-positive bacteria and the occasional Gram-negative bacterium or Archaea, where cell wall LPXTG-mediated decoration has not been reported. Although sortase A, the "housekeeping" sortase, typically acts on many protein targets, other forms of sortase recognize variant forms of the cleavage motif, or catalyze the assembly of pilins into pili.
The asd RNA motif is a conserved RNA structure found in certain lactic acid bacteria. The asd motif was detected by bioinformatics and an individual asd RNA in Streptococcus pyogenes was detected by microarray and northern hybridization experiments as a 170-nucleotide molecule called "SR914400". The transcription start site determined for SR914400 corresponds to the 5′-end of the molecule shown in the consensus diagram.
Bacterial small RNAs (bsRNA) are small RNAs produced by bacteria; they are 50- to 500-nucleotide non-coding RNA molecules, highly structured and containing several stem-loops. Numerous sRNAs have been identified using both computational analysis and laboratory-based techniques such as Northern blotting, microarrays and RNA-Seq in a number of bacterial species including Escherichia coli, the model pathogen Salmonella, the nitrogen-fixing alphaproteobacterium Sinorhizobium meliloti, marine cyanobacteria, Francisella tularensis, Streptococcus pyogenes, the pathogen Staphylococcus aureus, and the plant pathogen Xanthomonas oryzae pathovar oryzae. Bacterial sRNAs affect how genes are expressed within bacterial cells via interaction with mRNA or protein, and thus can affect a variety of bacterial functions like metabolism, virulence, environmental stress response, and structure.
RivX sRNA is a non-coding RNA molecule involved in the interface between two key regulators of virulence in the human pathogen Streptococcus pyogenes : the CovR/S system and Mga regulator. This RNA, along with its downstream protein-coding gene RivR, are the first discovered links between these two important regulation networks. An extra protein linking the two pathways, TrxR, was described a year later. The adjoining of these two pathways could allow a consistently high virulence of S. pyogenes despite a variety of environmental conditions.
Bacteriophage T12 is a bacteriophage that infects Streptococcus pyogenes bacteria. It is a proposed species of the family Siphoviridae in the order Caudovirales also known as tailed viruses. It converts a harmless strain of bacteria into a virulent strain. It carries the speA gene which codes for erythrogenic toxin A. speA is also known as streptococcal pyogenic exotoxin A, scarlet fever toxin A, or even scarlatinal toxin. Note that the name of the gene "speA" is italicized; the name of the toxin "speA" is not italicized. Erythrogenic toxin A converts a harmless, non-virulent strain of Streptococcus pyogenes to a virulent strain through lysogeny, a life cycle which is characterized by the ability of the genome to become a part of the host cell and be stably maintained there for generations. Phages with a lysogenic life cycle are also called temperate phages. Bacteriophage T12, proposed member of family Siphoviridae including related speA-carrying bacteriophages, is also a prototypic phage for all the speA-carrying phages of Streptococcus pyogenes, meaning that its genome is the prototype for the genomes of all such phages of S. pyogenes. It is the main suspect as the cause of scarlet fever, an infectious disease that affects small children.
In molecular biology, cia-dependent small RNAs (csRNAs) are small RNAs produced by Streptococci. These RNAs are part of the regulon of the CiaRH two-component regulatory system. Two of these RNAs, csRNA4 and csRNA5, have been shown to affect stationary-phase autolysis.
In molecular biology, the FasX small RNA (fibronectin/fibrinogen-binding/haemolytic-activity/streptokinase-regulator-X) is a non-coding small RNA (sRNA) produced by all group A Streptococcus. FasX has also been found in species of group D and group G Streptococcus. FasX regulates expression of secreted virulence factor streptokinase (SKA), encoded by the ska gene. FasX base pairs to the 5' end of the ska mRNA, increasing the stability of the mRNA, resulting in elevated levels of streptokinase expression. FasX negatively regulates the expression of pili and fibronectin-binding proteins on the bacterial cell surface. It binds to the 5' untranslated region of genes in the FCT-region in a serotype-specific manner, reducing the stability of and inhibiting translation of the pilus biosynthesis operon mRNA by occluding the ribosome-binding site through a simple Watson-Crick base-pairing mechanism.
RopB transcriptional regulator, also known as RopB/Rgg transcriptional regulator is a transcriptional regulator protein that regulates expression of the extracellularly secreted cysteine protease streptococcal pyrogenic exotoxin B (speB) [See Also: erythrogenic toxins] which is an important virulence factor of Streptococcus pyogenes and is responsible for the dissemination of a host of infectious diseases including strep throat, impetigo, streptococcal toxic shock syndrome, necrotizing fasciitis, and scarlet fever. Functional studies suggest that the ropB multigene regulon is responsible for not only global regulation of virulence but also a wide range of functions from stress response, metabolic function, and two-component signaling. Structural studies implicate ropB's regulatory action being reliant on a complex interaction involving quorum sensing with the leaderless peptide signal speB-inducing peptide (SIP) acting in conjunction with a pH sensitive histidine switch.
References
- ↑ Tsui HC, Mukherjee D, Ray VA, Sham LT, Feig AL, Winkler ME (January 2010). "Identification and characterization of noncoding small RNAs in Streptococcus pneumoniae serotype 2 strain D39". Journal of Bacteriology. 192 (1): 264–279. doi:10.1128/JB.01204-09. PMC 2798261 . PMID 19854910.
- ↑ Kumar R, Shah P, Swiatlo E, Burgess SC, Lawrence ML, Nanduri B (June 3, 2010). "Identification of novel non-coding small RNAs from Streptococcus pneumoniae TIGR4 using high-resolution genome tiling arrays". BMC Genomics. 11: 350. doi: 10.1186/1471-2164-11-350 . PMC 2887815 . PMID 20525227.
- 1 2 Mann B, van Opijnen T, Wang J, Obert C, Wang YD, Carter R, McGoldrick DJ, Ridout G, Camilli A, Tuomanen EI, Rosch JW (2012). "Control of virulence by small RNAs in Streptococcus pneumoniae". PLOS Pathog. 8 (7): e1002788. doi: 10.1371/journal.ppat.1002788 . PMC 3395615 . PMID 22807675.
- ↑ Acebo, Paloma; Martin-Galiano, Antonio J.; Navarro, Sara; Zaballos, Angel; Amblar, Mónica (March 2012). "Identification of 88 regulatory small RNAs in the TIGR4 strain of the human pathogen Streptococcus pneumoniae". RNA. 18 (3): 530–546. doi:10.1261/rna.027359.111. PMC 3285940 . PMID 22274957.
- ↑ Perez N, Treviño J, Liu Z, Ho SC, Babitzke P, Sumby P (November 2, 2009). "A genome-wide analysis of small regulatory RNAs in the human pathogen group A Streptococcus". PLOS ONE. 4 (11): e7668. Bibcode:2009PLoSO...4.7668P. doi: 10.1371/journal.pone.0007668 . PMC 2765633 . PMID 19888332.
- ↑ Mraheil MA, Billion A, Kuenne C, Pischimarov J, Kreikemeyer B, Engelmann S, Hartke A, Giard JC, Rupnik M, Vorwerk S, Beier M, Retey J, Hartsch T, Jacob A, Cemič F, Hemberger J, Chakraborty T, Hain T (November 2010). "Comparative genome-wide analysis of small RNAs of major Gram-positive pathogens: from identification to application". Microbial Biotechnology. 3 (6): 658–676. doi:10.1111/j.1751-7915.2010.00171.x. PMC 3815340 . PMID 21255362.
- ↑ Patenge N, Billion A, Raasch P, Normann J, Wisniewska-Kucper A, Retey J, Boisguérin V, Hartsch T, Hain T, Kreikemeyer B (October 13, 2012). "Identification of novel growth phase- and media-dependent small non-coding RNAs in Streptococcus pyogenes M49 using intergenic tiling arrays". BMC Genomics. 13: 550. doi: 10.1186/1471-2164-13-550 . PMC 3542284 . PMID 23062031.
- ↑ Pichon C, du Merle L, Caliot ME, Trieu-Cuot P, Le Bouguénec C (April 2012). "An in silico model for identification of small RNAs in whole bacterial genomes: characterization of antisense RNAs in pathogenic Escherichia coli and Streptococcus agalactiae strains". Nucleic Acids Research. 40 (7): 2846–2861. doi:10.1093/nar/gkr1141. PMC 3326304 . PMID 22139924.
- ↑ Xia L, Xia W, Li S, Li W, Liu J, Ding H, Li J, Li H, Chen Y, Su X, Wang W, Sun L, Wang C, Shao N, Chu B (June 2012). "Identification and expression of small non-coding RNA, L10-Leader, in different growth phases of Streptococcus mutans". Nucleic Acid Therapeutics. 22 (3): 177–186. doi:10.1089/nat.2011.0339. PMID 22468692.
- ↑ Liu Z, Treviño J, Ramirez-Peña E, Sumby P (October 2012). "The small regulatory RNA FasX controls pilus expression and adherence in the human bacterial pathogen group A Streptococcus". Molecular Microbiology. 86 (1): 140–154. doi:10.1111/j.1365-2958.2012.08178.x. PMC 3456998 . PMID 22882718.
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