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Xochitecatl [ʃot͡ʃiˈtekat͡ɬ] is a pre-Columbian archaeological site located in the Mexican State of Tlaxcala, 18 km southwest of Tlaxcala city. [1] The major architecture dates to the Middle Preclassic Period (1000–400 BC) but occupation continued, with one major interruption, until the Late Classic , when the site was abandoned.
The bacterial cell wall differs from that of all other organisms by the presence of peptidoglycan which is located immediately outside of the cell membrane. Peptidoglycan is made up of a polysaccharide backbone consisting of alternating N-Acetylmuramic acid (NAM) and N-acetylglucosamine (NAG) residues in equal amounts.
Glycocalyx is produced by many bacteria to surround their cells, [89] and varies in structural complexity: ranging from a disorganised slime layer of extracellular polymeric substances to a highly structured capsule. These structures can protect cells from engulfment by eukaryotic cells such as macrophages (part of the human immune system). [90]
Some research was made to identify the pyocins and show how they are involved in the “cell-to-cell” competition of the closely related Pseudomonas bacteria. The two types of tailocins differ by their structure; they are both composed of a sheath and a hollow tube forming a long helicoidal hexameric structure attached to a baseplate.
Structure of a teichoic acid repeat unit from Micrococcaceae Structure of the lipoteichoic acid polymer. Teichoic acids (cf. Greek τεῖχος, teīkhos, "wall", to be specific a fortification wall, as opposed to τοῖχος, toīkhos, a regular wall) [1] are bacterial copolymers [2] of glycerol phosphate or ribitol phosphate and carbohydrates linked via phosphodiester bonds.
The glycocalyx is located on the apical surface of vascular endothelial cells which line the lumen.When vessels are stained with cationic dyes such as Alcian blue stain, transmission electron microscopy shows a small, irregularly shaped layer extending approximately 50–100 nm into the lumen of a blood vessel.
L-form bacteria that lack a cell wall do not require FtsZ for division, which implies that bacteria may have retained components of an ancestral mode of cell division. [ 16 ] Much is known about the dynamic polymerization activities of tubulin and microtubules , but little is known about these activities in FtsZ.
It is primarily found in Gram-negative bacteria, such as Escherichia coli and Salmonella typhimurium. [1] Enterobactin is the strongest siderophore known, binding to the ferric ion (Fe 3+) with affinity K = 10 52 M −1. [2] This value is substantially larger than even some synthetic metal chelators, such as EDTA (K f,Fe3+ ~ 10 25 M −1). [3]