Lactic acid bacteria are a heterogeneous group of microorganisms that convert carbohydrates into lactic acid. They comprise both pathogens (such as Streptococcus pneumoniae or Streptococcus pyogenes) and useful bacteria (such as Streptococcus thermophilus and Lactococcus lactis (L. lactis), which were used for millennia in milk fermentation). In nature, L. lactis occupies a niche related to plant or animal surfaces and the animal gastrointestinal tract. It is believed to be dormant on the plant surfaces and to multiply in the gastrointestinal tract after being swallowed by a ruminant. In contrast, "domesticated" species of L. lactis, used by dairy industry as starters in cheese fermentation, live in a different niche, which is defined by technological[..]

Listeria monocytogenes(L. monocytogenes) is a Gram-positive facultative intracellular bacterial pathogen that elicits a strong cellular immune response following infection and therefore has potential use as a vaccine vector. However, while infections by L. monocytogenes are fairly rare and can readily be controlled by a number of antibiotics, the organism can nevertheless cause meningitis and death, particularly in immunocompromised or pregnant patients. L. monocytogenes EGD-e (Serovar 1/2a) is a derivative of strain EGD (Ref.1). As in most Gram-positive bacteria, the cell wall of L. monocytogenes is composed of a thick peptidoglycan containing two types of anionic polymers: (i) the TAs (Teichoic Acids), which are covalently linked to the peptidoglycan; and (ii) the[..]

Ralstonia solanacearum (previously named Pseudomonas solanacearum) is a devastating, soil-borne plant pathogen and the causal agent of bacterial wilt, one of the most important bacterial diseases worldwide. Hundreds of different plant species, including many important agricultural crops such as potato, tomato, banana, pepper, and even trees such as eucalyptus are affected by this vascular pathogen (Ref.1). It is a model system for the dissection of molecular determinants governing pathogenicity. It exhibits a strong and tissue-specific tropism within the host, specifically invading, and highly multiplying in, the xylem vessels of the roots. R. solanacearum is a Beta-Proteobacterium and thus belongs to a group of bacteria whose genomic organization is still poorly[..]

Photorhabdus sp. are facultatively anaerobic gram negative rods, nonsporulating and chemoorganotrophic heterotrophs with respiratory and fermentative metabolisms. They are included in the family of Enterobacteriaceae belonging to Group-5 and Sub-group1. Almost all species of Photorhabdus are entomopathogenic. The bacterium Photorhabdus luminescens is pathogenic to a wide range of insects (Ref.1). Bacteria cells are surrounded by a protective exoskeleton called the , peptidoglycan layer which is a cross-linked mesh-like macromolecule consisting of glycan strands interlinked by short peptides. A key step in peptidoglycan layer assembly and deposition in this bacterial cell wall is the subsequent enzymic cross-linking of one peptidoglycan strand to an adjacent one in cell[..]

Sinorhizobium meliloti (formerly Rhizobium meliloti), is a common Gram-negative soil and rhizosphere bacterium, that forms nitrogen-fixing nodules on the roots of certain genera of leguminous plants, including Medicago, Melilotus and Trigonella sp. Inside the nodules, differentiated bacteria called bacteroids fix atmospheric nitrogen (i.e. reduce N2 into NH3) to the benefit of the plant. Nodule formation and the subsequent nitrogen-fixation result from a series of interactions controlled by the exchange of molecular signals between symbiotic bacteria and host plants followed by expression of genes from both symbiotic partners. S. meliloti surface polysaccharides, including exopolysaccharides, lipopolysaccharides, capsular polysaccharides, and cyclic Beta-Glucans are[..]

Oceanobacillus iheyensis is an alkaliphilic and extremely halotolerant Bacillus-related species isolated from deep-sea sediment. It is also known as 'small ocean bacillus pertaining to the Iheya Ridge' from where it was isolated. O. iheyensis grows at depths of up to 3,000 m. The bacteria thrive under high hydrostatic pressure and grow optimally at about 30 degrees Celsius (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 peptidoglycan layer assembly and deposition is the[..]

The Alpha-Proteobacteria is predominantly responsible for the degradation of organosulfur compounds, including the algal osmolyte dimethylsulfoniopropionate. Silicobacter pomeroyi carries out many organic sulfur transformations that occur in natural bacterial communities in the surface ocean. The bacterium converts dimethylsulfoniopropionate to both dimethylsulfide and methanethiol. Through these pathways, the sulfur in dimethylsulfonio propionate is either released as volatile sulfur to the atmosphere, or retained in the marine food web in the form of S-containing amino acids (Ref.1 & 2). The cell wall of these bacteria is a unique biopolymer, containing both D- and L-Amino acids. The terminal peptide is D-Alanine although other amino acids are present as[..]

Nitrosomonas europaea is a Gram-negative obligate chemolithoautotroph, which derives all its energy and reductant for growth from the aerobic oxidation of ammonia to nitrite. The bacterium participates in the biogeochemical Nitrogen cycle in the process of nitrification (Ref.1). A key step in peptidoglycan layer assembly and deposition in the cell wall of N.europaea is the subsequent enzymic cross-linking of one peptidoglycan strand to an adjacent one in cell wall growth. D-Alanine is a central molecule in this peptidoglycan assembly and cross-linking. 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. The naturally occurring[..]

Methanotrophs are a unique group of Gram-negative bacteria that grow aerobically on methane and utilize methane as the sole source of carbon and energy. Methanotrophs such as Methylococcus capsulatus(M. capsulatus) are responsible for the oxidation of biologically generated methane, and they are therefore of great environmental importance in reducing the amount of this greenhouse gas released to the Earth's atmosphere (Ref.1). A key step in peptidoglycan layer assembly and deposition in the cell wall of M. capsulatus is the subsequent enzymic cross-linking of one peptidoglycan strand to an adjacent one in cell wall growth. D-Alanine is a central molecule in this peptidoglycan assembly and cross-linking (Ref.2). L-Alanine is also a product of several other metabolic[..]

Streptococcus thermophilus is one of the most economically important lactic acid bacteria used in the manufacture of yogurt and cheeses. This bacterium belongs to the group of GRAS (Generally Recognized as Safe) bacteria which is an exception in the Streptococcus genus. S. thermophilus is used, along with Lactobacillus sp., as a starter culture for the manufacture of several important fermented dairy foods, including yogurt and Mozzarella cheese. Its use has increased significantly during the past two decades, as a result of the tremendous increase in consumption of these products (Ref. 1 & 2).The cell wall of these Gram-positive bacteria constitutes a multifaceted fabric that is essential for survival, shape, and integrity. D-Alanine occurs to the extent of 1 to 2[..]

Rhizobium, Bradyrhizobium, Mesorhizobium, Sinorhizobium and Azorhizobium-known as Rhizobia-are Gram-negative, nitrogen-fixing bacteria of agronomic importance because they perform nitrogen-fixing symbiosis with leguminous plants. Nodule formation and the subsequent nitrogen-fixation result from a series of interactions controlled by the exchange of molecular signals between symbiotic bacteria and host plants followed by expression of genes from both symbiotic partners. Mesorhizobium loti (M .loti) is able to form determinant-type globular nodules and perform nitrogen-fixation on several Lotus species (Ref.1).The cell wall of these Gram-negative bacteria constitutes a multifaceted fabric that is essential for survival, shape, and integrity. Macromolecular assemblies of[..]

Streptococcus thermophilus is one of the most economically important lactic acid bacteria used in the manufacture of yogurt and cheeses. This bacterium belongs to the group of GRAS (Generally Recognized As Safe) bacteria which is an exception in the Streptococcus genus. S. thermophilus is used, along with Lactobacillus sp., as a starter culture for the manufacture of several important fermented dairy foods, including yogurt and Mozzarella cheese. Its use has increased significantly during the past two decades, as a result of the tremendous increase in consumption of these products (Ref. 1 & 2).The cell wall of these Gram-positive bacteria constitutes a multifaceted fabric that is essential for survival, shape, and integrity. D-Alanine occurs to the extent of 1 to 2[..]