Streptococcus pneumoniae (also known as Pneumococcus or Diplococcus pneumoniae) is a Gram-positive coccus and is among the most significant causes of bacterial disease in humans. It is responsible for a high proportion of cases of pneumonia, acute otitis media, acute sinusitis, bacteremia and meningitis. There are 90 known serotypes of S. pneumoniae, each of which produces a structurally different capsular polysaccharide; during infection. These serotypes function by inhibiting host complement-mediated phagocytosis. The parental S. pneumoniae strain for R6 is R36A, which is a nonencapsulated strain is derived from the capsular Type 2 clinical isolate strain D39. The pneumococcal plasma membrane is surrounded by a layer of peptidoglycan, a three-dimensional,[..]

Based on differences in their compositions and the linkages of cell wall polysaccharides, Streptococci are classified into eight serotypes as follows; Streptococcus mutans (Serotypes c, e, and f), Streptococcus sobrinus (Serotypes d and g), Streptococcus cricetus (Serotype a), Streptococcus rattus (Serotype b), Streptococcus ferus (Serotype c), Streptococcus macacae (Serotype c), and Streptococcus downei (Serotype h). Among these, S. mutans is known to be a major causative bacterium of dental caries in humans and is occasionally isolated from the blood of patients with infective endocarditis (Ref.1). The cell wall of this bacterium is a peptidoglycan macromolecule with attached accessory molecules such as TAs (Teichoic Acids), Teichuronic Acids, LTA (Lipoteichoic[..]

Staphylococcus epidermidis is a Gram-positive non motile bacterium that grows in aerobic and anaerobic conditions, in which it forms grape-like clusters. It produces numerous toxins including superantigens that cause unique disease entities and has emerged as a causative agent of infections often associated with implanted medical devices. The S. aureus and S. epidermidis genomes are syntenic throughout their lengths and share a core set of 1,681 ORF (Open Reading Frames) (Ref.1 & 2).The cell wall of S. epidermidis is 50 percent peptidoglycan by weight consisting of alternating polysaccharide subunits of N-Acetylglucosamine and N-Acetylmuramic acid with 1, 4-Beta linkages. The peptidoglycan chains are cross-linked by tetrapeptide chains bound to N-Acetylmuramic acid[..]

Staphylococci are known as clustering Gram-positive cocci, nonmotile, non-spore forming facultatively anaerobic that classified in two main groups, coagulase-positive and coagulase-negative. Staphylococcus epidermidis with the highest percentage has the prominent role among coagulase-negative Staphylococci that is the most important reason of clinical infections. Staphylococcus, is one of the five significant microorganisms that are located on human skin and mucosal surfaces with the ability of causing nosocomial infections due to the wide usage of medical implants and devices, hence until 1980 S. epidermidis was considered as an opportunistic microorganism, while in accordance to various infections increasement such as cardiovascular, CNS shunts,[..]

The Group-A Streptococcus (Streptococcus pyogenes) remains an important human pathogen, associated with a range of superficial skin and throat infections as well as a variety of more serious invasive infections and autoimmune sequelae such as acute rheumatic fever and post-streptococcal glomerulonephritis (Ref.1). S. pyogenes strains are grouped into two classes on the basis of post infectious sequelae associated with each strain, Class-I is responsible for rheumatic fever and Class-II is responsible for acute glomerulonephritis. S. pyogenes strain SF370 (Serotype M1) was originally isolated from a patient with a wound infection. The Serotype M1 is among the most prevalent in terms of involvement in severe invasive infections (Ref.2 & 3).As is the case in other[..]

Streptococcus agalactiae, or Group-B Streptococcus is a Gram-positive nonmotile bacterium and is the leading cause of bacterial sepsis, pneumoniae and meningitidis in neonates in U.S. and Europe. It usually behaves as a commensal organism that colonizes the gastrointestinal or genital tract of 25-40% of healthy women, but it can cause life-threatening invasive infection in susceptible hosts: newborn infants, pregnant women, and adults with underlying chronic illnesses. First recognized as a pathogen in bovine mastitis, S. agalactiae (Group-B Streptococci [GBS]) is distinguished from other pathogenic streptococci by the cell wall-associated group B carbohydrate. S. agalactiae strain NEM316 is responsible for a fatal septicemia and belongs to the Capsular Serotype-II. It[..]

Bacteria of the genus Brucella are Gram-negative facultative intracellular pathogens of various wild and domestic mammals and are able to cause brucellosis, a severe zoonotic infection affecting ruminants, pigs, dogs, rodents, and cetacean. Traditionally, three major species are distinguished by their predilections for certain animal hosts: Brucella abortus for cattle, Brucella melitensis for caprines, and Brucella suis for hogs. Whereas B. abortus is the livestock pathogen with the greatest economic impact, B. melitensis and B. suis account for most clinical cases in humans (Ref.1). Human brucellosis, or Malta fever, is a serious debilitating disease that is rife in endemic areas including the Mediterranean basin and Latin America. The key aspect of Brucella virulence[..]

The Clostridia are a diverse group of Gram-positive, rod-shaped anaerobes that include several toxin-producing pathogens (notably Clostridium difficile, Clostridium botulinum, Clostridium tetani, Clostridium acetobutylicum and Clostridium perfringens) and a large number of terrestrial species that produce acetone, butanol, ethanol, isopropanol, and organic acids through fermentation of a variety of carbon sources. C. acetobutylicum strain ATCC 824 has been used for the industrial production of acetone, butanol, and ethanol by the fermentation of carbohydrates. This organism is able to utilize a wide range of carbohydrate substrates, including the polymers starch and xylan and saccharides such as glucose, xylose, and cellobiose (Ref.1). The cell wall of C.[..]

Caulobacter crescentus is a Gram-negative non-pathogenic bacterium that grows in dilute aquatic environments. It is a member of the Alpha-subdivision of Proteobacteria. C. crescentus invariably differentiates and divides asymmetrically at each cell cycle. C. crescentus is a simple and highly manipulable single-celled model system to study cellular differentiation, asymmetric division, and their coordination with Cell Cycle progression (Ref.1). The cell wall of this bacterium is a unique biopolymer, containing both D- and L-Amino acids. The terminal peptide is D-Alanine although other amino acids are present as D-isomers and this is the only known biological molecule that contains D-Amino acids, which are responsible for the building of peptidoglycan. A key step in[..]

The bacterial cell wall is a unique biopolymer, containing both D- and L-Amino acids. Its basic structure is a carbohydrate backbone of alternating units of N-Acetyl Glucosamine and N-Acetyl Muramic Acid. The N-Acetyl Muramic Acid residues are cross-linked with oligopeptides. The terminal peptide is D-Alanine although other amino acids are present as D- isomers and this is the only known biological molecule that contains D-Amino acids, which are responsible for the building of peptidoglycan. The cell wall of Gram-positive bacteria is largely made up of pepidoglycan. A key step in peptidoglycan layer assembly and deposition is the subsequent enzymic cross-linking of one peptidoglycan strand to an adjacent one in cell wall growth. Protonated D-Alanyl Ester residues, one[..]

Enterococci are Gram-positive, facultative anaerobic and lactic acid producing bacteria. Most strains are nonhemolytic. Enterococcus faecalis (also known as Streptococcus faecalis), the second most frequent enterococcal species, is a saprophytic commensal that inhabits the oral cavity and gastrointestinal flora of humans and animals, although it can behave as an opportunistic pathogen causing severe urinary tract infections, surgical wound infections, bacteremia, and bacterial endocarditis. Over the past 2 decades, E. faecalis has become responsible for up to 12% of nosocomial infections, with mortality rates for bloodstream infections ranging from 20 to 68% depending on the patient population. The increased incidence of E. faecalis infection has been related to the[..]

Erwinia carotovora is a member of the “soft-rot” group of Erwinias and is capable of causing tissue maceration and disease among a broad host range of plants, especially potato tubers held in storage. D-Alanine is a necessary precursor in the biosynthesis of peptidoglycan layer in Erwinia carotovora. The naturally occurring L-Alanine isomer is racemized to its D-form through the action of a class of enzymes called AlRs (Alanine Racemase). This enzyme is ubiquitous among prokaryotes and with very few exceptions are absent in eukaryotes. All known bacteria require D-Alanine, whereas only L-Alanine is used in mammalian protein synthesis. L-Alanine is also a product of several other metabolic pathways like Cyanoamino Acid Metabolism, Selenoamino Acid[..]