Gram-positive bacteria cytoplasmic membrane

As described in Section II,A, gram-positive bacteria have only one membrane (the cytoplasmic membrane). Therefore, the translocation through the Sec pathway directly leads proteins to be secreted (Simonen and Palva, 1993 Nagarajan, 1993). The issue of protein sorting into the cell wall is described in a separate section. 

Other inhibitors of cell wall synthesis. Bacitracin and vancomycin interfere with the transport of pepti-doglycans through the cytoplasmic membrane and are active only against gram-positive bacteria. Bacitracin is a polypeptide mixture, markedly nephrotoxic and used only topically. Vancomycin is a glycopeptide and the drug of choice for the (oral) treatment of bowel inflammations occurring as a complication of antibiotic therapy (pseudomembranous enterocolitis caused by Clostridium difficile), it is not absorbed. 

Beta-lactam antibiotics must pass through the outer layer of the cell in order to get the desired PBP to the surface of the membrane. In Gram-positive bacteria, the cell membrane is the only layer covering the cytoplasmic membrane. In a few types of this bacteria, there is a polysaccharide capsule on the outer side of the cell membrane. However, not one of the described structures can serve as a barrier for the diffusion of small molecules such as beta-lactams. Therefore, the idea that the cause of possible resistance is the inability of beta-lactam antibiotics to get the desired PBP is not likely to be a possible mechanism of resistance for Gram-positive bacteria. 

Halococcus morrhuae forms single cells or cuboidal packets. The cells are surrounded by one electron-dense layer outside the cytoplasmic membrane, 50-60 nm in width (Fig. 8). This layer forms a rigid cell wall sacculus [79] and tends to become laminated as was also observed for Methanosarcina barkeri [61,64]. The rigid cell-wall sacculi prevent lysis of the cocci in media with low ionic strength and have been isolated by the usual techniques applied for gram-positive bacteria [80]. 

The characteristic components of the cytoplasmic membrane of Gram-positive bacteria are the amphiphilic macromolecules lipoglycan and lipoteichoic acid [39,40] (O Fig. 8). Lipotei-choic acids possess in their saccharide chain alditol phosphates as characteristic components, whereas lipoglycans are linear or branched polysaccharides linked to diacylglycerol. These molecules may be further substituted by phosphoglycerol residues. Since lipoteichoic acids and lipoglycans are not found in the same bacterium they are believed to replace each other... 

Bacterial copper proteins are found only in the plasma membrane (Gram-positive bacteria) or in the plasma membrane and the periplasm (Gram-negative bacteria), not in the bacterial cytoplasm. However, cyanobacteria do have copper proteins in their cytoplasm. These important photosynthetic bacteria require copper for plastocyanin, which plays a critical role in the photosynthetic electron transport chain. Both plastocyanin and cytochrome c oxidase are found in the thylakoid compartments within the cytoplasm. In Synechocystis, the Cu(I) Pie-ATPase CtaA imports Cu(I). A second ATPase, PacS, imports Cu(I) into the thylakoid, and the Atxl-like copper chaperone ScAtxl is believed to deliver Cu(I) from CtaA to PacS (Fig. 8.6). 

Gram-positive bacteria (e.g.. Staphylococcus aureus) are surrounded by a cytoplasmic membrane with a bilayer... 

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