The peptidoglycan sacculus is the stress-bearing structure of bacterial cells. It consists of glycan strands cross-linked by peptide bridges. Peptidoglycan, or murein as it is also known, is a polymer consisting of sugars and amino acids that forms a mesh-like layer outside the plasma membrane of bacteria. The sugar component consists of alternating residues of β-(1,4) linked N-acetylglucosamine and N-acetylmuramic acid residues. Attached to the N-acetylmuramic acid is a peptide chain of three to five amino acids. The peptide chain can be cross-linked to the peptide chain of another strand forming the three-dimensional mesh-like layer.

The peptidoglycan layer is much thicker in Gram-positive bacteria than in Gram-negative bacteria.

Peptidoglycan biosynthesis is the target for many antibiotics such as β-lactams, D-cycloserine and glycopeptide-antibiotics such as vancomycin. Bacteria have developed a number of different antibiotic resistance mechanisms for coping with these antibiotics.


Further reading:
Bacterial Polysaccharides
Biopolymers and Polymer Precursors

Labels: biopolymers, Gram-positive bacteria, peptidoglycan, polysaccharides

Acanthamoeba is a type of amoeba that lives in the environment, in the soil, in fresh water and in other habitats. Acanthamoeba rarely causes infections but when it does cause infection, however, it can be extremely serious. Diseases caused by Acanthamoeba include amoebic keratitis and encephalitis. Encephalitis is caused by Acanthamoeba entering cuts and spreading to the central nervous system. Amoebic keratitis is a rare disease where the amoebae (Acanthamoeba) invade the cornea of the eye. Recently, there have been multiple reports of increasing incidence of Acanthamoeba keratitis especially among contact lens wearers.

Further reading: Acanthamoeba: Biology and Pathogenesis
See also: Acanthamoeba pictures, illustrations and figures

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Microbiology is the study of tiny living organisms. These can be single cell microscopic organisms or microscopic organisms consisting of many cells. Microbiology includes the study of eukaryotes such as fungi and protists but is mainly concerned with the study of prokaryotes such as bacteria and certain algae. Viruses are also included. Microbiology is subdivided into branches including bacteriology, virology, mycology, parasitology and others.

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