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Gram positive

2018-10-17T15:46:29Z

170726382:

The Gram-positive [[Bacteria|bacterial]] [[Cell wall|cell wall]] is one of the two types of bacterial cell walls the other being [[Gram negative|Gram-negative]] cell walls. The Gram-positive cell walls are mainly composed of [[Peptidoglycan|peptidoglycan]] although they also consist of the surface [[Proteins|proteins]], [[Teichoic acids|teichoic]] and [[Lipoteichoic acid|lipoteichoic acids]] the latter of which connects the cell wall to the cell membrane. The teichoic and lipoteichoic acids contribute to the positive charge of the bacterial cell surface and they are [[Glycerophosphate|glycerophosphate]] or [[Ribitol phosphate|ribitol phosphate]]- containing acidic polysaccharides.

The thick layer of peptidoglycan enables the cell wall to retain the purple colour of [[Crystal violet|crystal violet]] upon constriction consequent upon treatment with [[Iodine|iodine]]. Thus Gram-positive bacterial cell walls stain purple.

Examples of Gram-positive bacteria include ''[[Staphylococcus aureus|Staphylococcus aureus]]'', ''[[Streptococcus pyogenes|Streptococcus pyogenes]]'' and [[Streptococcus pneumonia|''Streptococcus pneumonia'']] amongst others<ref name="Kaiser, G.">Kaiser, G. (2012) The Prokaryotic Cell: Bacteria. http://faculty.ccbcmd.edu/courses/bio141/lecguide/unit1/prostruct/gpcw.html. The Community College of Baltimore County.</ref>.

=== The structure of the Gram-positive peptidoglycan cell wall ===

[[Peptidoglycan|Peptidoglycan]] is made from monomers called glycan tetrapeptides, these are linked together in chains which are in turn linked together. In gram-positive bacteria the crosslink is a [[Peptide|peptide]] interbridge which is different in its structure depending on the bacterial strain, in [[Staphylococcus aureus|Staphylococcus aureus]] the interbridge is made from five [[Glycine|glycine]] residues<ref>Madigan Micahel T, Martinko John M, Bender Kelly S, Buckley Daniel H, Stahl David A. “Brock biology of microorganisms” 14th edition, Pearson education limited, 2014.</ref>.

=== '''Characteristics''' ===

1) Cross-linked Peptidoglycan chains.<ref>https://www.life.umd.edu/classroom/bsci424/BSCI223WebSiteFiles/GramPosvsGramNeg.htm</ref>

2) Periplasm of a smaller volume in comparisson to that of gram-negeative bacteria.

3) A lipid membrane that is cytoplasmic.

<ref>Madigan, Michael T.; Martinko, John M. (2006). Brock Biology of Microorganisms (11th ed.). Pearson Prentice Hall. ISBN 0131443291.</ref>

 

=== Infections caused by Gram positive bacteria ===

Methicillin-Resistant Staph. Aureus (MSRA) and Vancomycin-Resistant Enterococcus (VRE) are one of the highly resistant Gram positive bacteria<ref>https://www.medscape.com/viewarticle/452426</ref>. The antibiotics that can be used to treat the infections caused by them are Vancomycin, Ceftaroline, etc<ref>https://www.medicalnewstoday.com/articles/10634.php</ref>. These inhibit cell wall synthesis and prevent the infections from spreading. Though Gram positive infections lead to limitations of availability of these antibiotics due to cost issues and antibiotic resistance<ref>http://onlinelibrary.wiley.com/doi/10.1046/j.1469-0691.2001.00064.x/full</ref>, these antibiotics, and few other like Linezolid which is an excellent example of bioavailability<ref>https://academic.oup.com/jac/article/66/suppl_4/iv7/729737</ref>, have been effective in treating the infections.

=== References ===

<references />

POLYPEPTIDES

2017-12-03T20:40:01Z

170726382:

A polypeptide is a polymer which is linear and consists of many amino acids bonded together via condensation reactions that result in peptide bonds between the amino acids, which are examples of covalent bonds. The polymer chain also contains two terminals; the carboxyl terminal at the end with a free carboxyl group and an amino terminal at the end with a free amino group <ref>Lubert Stryer, Biochemistry, fourth edition, W.H Freeman and Company New York 1955.</ref>. 

The amino acids contained within polypeptides themselves are coded for by codons which are also part of a ploymer known as messenger RNA, the processs of which is known as translation. However, before translation can occur, messenger RNA must be synthesised via complementary base pairing during transcription. This is dictated by the sequence of codons within DNA..

POLYPEPTIDES

2017-12-03T20:12:48Z

170726382:

A polypeptide is a polymer which is linear and consists of many amino acids bonded together via condensation reactions that result in peptide bonds between the amino acids, which are examples of covalent bonds. The polymer chain also contains two terminals; the carboxyl terminal at the end with a free carboxyl group and an amino terminal at the end with a free amino group<ref>Lubert Stryer, Biochemistry, fourth edition, W.H Freeman and Company New York 1955.</ref> . 

The amino acids contained within polypeptides themselves are coded for by codons which are also part of a ploymer known as messenger RNA, the processs of which is known as translation. However, before translation can occur, messenger RNA must be synthesised via complementary base pairing during transcription. This is dictated by the sequence of codons within DNA..

POLYPEPTIDES

2017-12-03T19:16:26Z

170726382: Created page with " A polypeptide is a polymer which is linear and consists of many amino acids bonded together via condensation reactions that result in peptide bonds between the amino acids,..."

A polypeptide is a polymer which is linear and consists of many amino acids bonded together via condensation reactions that result in peptide bonds between the amino acids, which are examples of covalent bonds. The polymer chain also contains two terminals; the carboxyl terminal at the end with a free carboxyl group and an amino terminal at the end with a free amino group[1]. 

The amino acids contained within polypeptides themselves are coded for by codons which are also part of a ploymer known as messenger RNA, the processs of which is known as translation. However, before translation can occur, messenger RNA must be synthesised via complementary base pairing during transcription. This is dictated by the sequence of codons within DNA..