Staphylococcus aureus are Gram-positive nonmotile coccus that grows in aerobic and anaerobic conditions, in which it forms grape-like clusters. S. aureus is an opportunistic pathogen and the major causative agent of numerous hospital- and community-acquired infections. It produces numerous toxins including super antigens that cause unique disease entities such as toxic-shock syndrome and staphylococcal scarlet fever. Its genetic plasticity has facilitated the evolution of many virulent and drug-resistant strains, presenting a major and constantly changing clinical challenge. S. aureus COL is an early methicillin-resistant isolate (Ref.1).The cell wall of S. aureus is 50 percent peptidoglycan by weight consisting of alternating polysaccharide subunits of[..]

Listeria monocytogenes(L. monocytogenes) is a Gram-positive bacterium widely spread in nature and responsible for sporadic severe infections in humans and other animal species. This pathogen is a facultative intracellular microorganism capable of invading and surviving in most host cells, including epithelial cells and macrophages. L. monocytogenes strain F2365 (Serotype 4b) has been isolated from Jalisco cheese outbreak in 1985 in California (Ref.1).The naturally occurring L-Alanine isomer is racemized to its D-form through the action of a class of enzymes called dal (alanine racemase). This enzyme is ubiquitous among prokaryotes and with very few exceptions are absent in eukaryotes. It catalyzes the racemization of L-Alanine and D-Alanine, using Pyridoxal[..]

Group-A Streptococcus pyogenes remains an important human pathogen responsible for a variety of suppurative infections, including pharyngitis, scarlet fever, impetigo, and cellulitis and for nonsuppurative sequelae, such as acute rheumatic fever, acute glomerulonephritis, and reactive arthritis (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 SSI-1 (Serotype M3) is among the most prevalent in terms of involvement in severe invasive infections (Ref.2 & 3).As is the case in other Gram-positive bacteria, the cell wall of S. pyogenes is associated with an array of proteins[..]

Lactic acid bacteria play important roles in food conservation because of their fermentative ability and contribute to the equilibrium of the gastrointestinal tract microbiota. Lactobacillus johnsonii (L. johnsonii)  is commonly found in the gastrointestinal tract and adhere to intestinal cells. Such interactions of bacteria with the gastrointestinal tract contribute to its protection against pathogenic microorganisms. A close association between the bacteria and their environment undoubtedly results in adaptation of their metabolic capacities (Ref.1).D-Alanine occurs to the extent of 1 to 2 per cent of the dry cells of various lactic acid bacteria including L. johnsonii and L-Alanine is essential for L. johnsonii growth. The naturally occurring L-Alanine isomer[..]

Symbiobacterium thermophilum is a symbiotic Gram-negative and tryptophanase-positive thermophile. It is an uncultivable bacterium isolated from compost that depends on microbial commensalism. It does not grow by itself under standard culture conditions; however, when cocultured with Bacillus sp., it propagates. S.thermophilum proliferates under both aerobic and anaerobic conditions (Ref.1, 2 & 3).The cell wall of this Gram-negative bacterium constitutes a multifaceted fabric that is essential for survival, shape, and integrity. Macromolecular assemblies of cross-linked peptidoglycan, polyanionic TAs (Teichoic Acids), and surface proteins function within this envelope. A key step in peptidoglycan layer assembly and deposition in the cell wall of S. thermophilum is[..]

Lactiplantibacillus plantarum (previously Lactobacillus plantarum) is a member of the facultative heterofermentative group of Gram-positive Lactobacilli that are frequently isolated from plant material and various fermented foods. Lactobacilli produce lactic acid and are used for many different things, including yogurt production and the maintenance of healthy intestinal microflora. Lactobacilli are commonly associated with the gastrointestinal tract of humans. L. plantarum is the dominating bacterial species in most naturally fermented foods. It is an excellent alternative to antibiotics, and makes use of its potential to block receptor sites for Gram-negative bacteria. L. plantarum is capable of metabolizing semi resistant fibers, such as, onions, garlic, artichoke,[..]

Legionella pneumophila is the causative agent of Legionnaires' disease, which replicates as an intracellular parasite of amoebae and persists in the environment as a free-living microbe (Ref.1). D-Alanine is a necessary precursor in the biosynthesis of cell wall in this bacterium. L-Alanine is also a product of several other metabolic pathways like Cyanoamino Acid Metabolism, Selenoamino Acid Metabolism, Alanine and Aspartate, and D-Arginine and D-Ornithine Metabolism(Ref.2). The naturally occurring L-Alanine isomer is racemized to its D-form through the action of a class of enzymes called alr (alanine racemase). This enzyme is ubiquitous among prokaryotes and with very few exceptions are absent in eukaryotes.alr belongs to the class of Isomerase enzymes,[..]

Bacilli are an extremely diverse group of bacteria that include both the causative agent of anthrax (Bacillus anthracis) as well as several species that synthesize important antibiotics. Bacilli are rod-shaped, Gram-positive, sporulating, aerobes or facultative anaerobes. Bacilli exhibit an array of physiologic abilities that allow them to live in a wide range of habitats, including many extreme habitats such as desert sands, hot springs, and Arctic soils. Species in the genus Bacillus can be thermophilic, psychrophilic, acidophilic, alkaliphilic, halotolerant, or halophilic and are capable of growing at pH values, temperatures, and salt concentrations where few other organisms can survive (Ref.1, 2 & 4). Due to the metabolic diversity in the genus Bacillus,[..]

Bacillus cereus is a gram-positive, facultative anaerobic rod-shaped endospore-forming bacterium. B. cereus occurs ubiquitously in soil and in many raw and processed foods such as rice, milk and dairy products, spices, and vegetables. Many strains of B. cereus are able to produce toxins and cause distinct types of food poisoning. B. cereus is an opportunistic pathogen causing food poisoning manifested by diarrhoeal or emetic syndromes. It is closely related to the animal and human pathogen Bacillus anthracis and the insect pathogen Bacillus thuringiensis, the former being used as a biological weapon and the latter as a pesticide (Ref.1&2).The cell wall of these Gram-positive bacteria is a unique biopolymer, containing both D- and L-Amino acids. Its basic structure[..]

The spore-bearing alkaliphilic Bacillus species constitute a large, heterogeneous group of microorganisms which are now being investigated in order to better understand the physiology, biochemistry, and especially molecular genetics underlying the behavior of alkaliphilic bacteria. As alkaliphilic Bacillus strains produce enzymes, such as xylanases, cellulases, amylases, and proteases, they are very useful in industry and domestic life. B. clausii is an alkalitolerant species of Bacillus (Ref.1, 2 & 3).The cell wall of these Gram-positive bacteria 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[..]

Bacillus licheniformis(B. licheniformis) is a Gram-positive, spore-forming soil bacterium that is used in the biotechnology industry to manufacture enzymes, antibiotics, biochemicals and consumer products. This species is closely related to B. subtilis, and produces an assortment of extracellular enzymes that may contribute to nutrient cycling in nature. Unlike most other Bacilli, which are predominantly aerobic, B. licheniformis is a facultative anaerobe, which may allow it to grow in additional ecological niches. The type strain ATCC 14580 consists of a circular chromosome best studied of all B. licheniformis strains (Ref.1).The cell wall of these Gram-positive bacteria is a unique biopolymer, containing both D- and L-Amino acids. Its basic structure is a[..]

Bacillus licheniformis(B. licheniformis) is a Gram-positive, spore-forming soil bacterium that is used in the biotechnology industry to manufacture enzymes, antibiotics, biochemicals and consumer products. B. licheniformis, B. subtilis, and B. pumilus comprise the subtilis group, which has been associated with a range of clinical conditions, food spoilage such as ropy bread, and incidents of food-borne gastroenteritis. B. licheniformis has also been associated with septicemia, peritonitis, ophthalmitis, and food poisoning in humans, as well as with bovine toxemia and abortions. It is a common contaminant of dairy products. B. licheniformis DSM13 consists of a single chromosome and has a well-conserved secretory system (Ref.1).The cell wall of these Gram-positive[..]