Gram-positive bacteria are the genus of bacteria family and a member of the phylum Firmicutes. These bacteria retain the color of the crystal violet stain which is used during gram staining procedure and these bacteria give a positive result in the Gram stain test by appearing purple-colored when examined under a microscope. Actinomyces, Clostridium, Mycobacterium, streptococci, staphylococci, and Nocardia are a few examples of gram-positive bacteria.
General characteristics features of Gram-positive bacteria
- They have a thick peptidoglycan layer and cytoplasmic lipid membrane.
- These bacteria lack an outer membrane.
- Have a lower lipid content and more teichoic acids.
- They move around with the help of locomotion organs such as cilia and flagella.
- The walls of Staphylococcus aureus and Streptococcus faecalis contain teichoic acid.
Gram-Positive Cell Walls
The composition of gram-positive bacteria cell wall includes:
It is permeable, cross-linked organic polymer and rigid structure which plays an important role in providing shape and strength to the cell wall. It makes up about 90% of the cell wall enclosing the plasma membrane and protects the cell from the environment. Peptidoglycan is composed of three main components including- Glycan backbone, Peptide, and Tetra-peptide.
The lipid element found in the gram-positive bacteria cell wall supports in its anchoring to the membrane. The total percentage of lipid content in gram-positive bacterium cell wall is 2 – 5 percentage.
It is water soluble and a polymer of glycerol. Teichoic acid is the major surface antigen of gram-positive bacteria and it makes up about fifty percent of the total dry weight of the cell wall.
Benefits of Gram-positive bacteria
- These species of bacteria are non-pathogenic which resides within our body including the mouth, skin, intestine, and upper respiratory tract.
- They are an essential ingredient in producing Emmentaler or Swiss cheese.
- The species of Corynebacterium are used in industrial production of enzymes, amino acids, nucleotides, etc.
- Various Bacillus species are used in the secretion of large quantities of enzymes.
- Few species of gram-positive bacteria are also involved in the cheese aging, bioconversion of steroids, degradation of hydrocarbons, etc.
- Bacillus amyloliquefaciens of gram-positive bacteria are the good source of a natural antibiotic protein – Barnase.
Risk factors of gram-positive bacteria
The substantial increase in skin and mucous infections in all humans are caused by staphylococcal species. These organisms are mainly transmitted through skin contact, fomite contact, by inhaling of infected aerosolized particles, by pets, etc. Other risk factors include food poisoning, Respiratory Diseases, tooth cavities, Diphtheria, Mycobacterium tuberculosis, etc.
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