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what are endospores and describe ( structure and function) and Why might endospores give a species of bacteria a competitive advantage and What primary and secondary stain will we be using during the endospore stain?

Answer 1

Q) What are endospores and describe (structure and function) and why might endospores give a species of bacteria a competitive advantage and What primary and secondary stain will we be using the endospore stain?

Ans) Endospore is a metabolically dormant and non-reproductive structure produced by the bacteria belongs to the phylum Firmicute and they do not exhibit any signs of life so they are called as cryptobiotic. They are produced by gram-positive bacteria under unfavorable conditions during late log phase or early stationary phase by a process called sporulation. The typical spore size is 0.2 µm and it shows resistance to temperature, extreme pH, antibiotics, UV, lysozyme and chemical disinfectants.

endospore made up of four layers

1) Exosporium: it is the outer most layer of the spore which interacts with the environment and it has antigens. It is made up of the protein, polysaccharide, and lipids. In B. anthracis and B.cereus made up of Cot protein.

2) Spore coat: it is thick double-layered structure cover the cortex and made up of cysteine and hydrophobic amino acids which make them more resistant towards harsh environmental conditions and chemical agents.

3) Cortex: layer beneath the spore coat is called cortex and made up of loosely arranged peptidoglycan. The inner layer of cortex made up of 20% of peptidoglycan & outer layer of cortex made up of alanine (55%), tetra-peptide (15%) and muramic lactum (30%) and this layer is hydrolyzed during spore germination.

4) Core: it is the innermost layer of the spore and also known as spore protoplast made up of core wall, cytoplasmic membrane, cytoplasm, nucleoid, ribosomes and 10-25% water. Chemically it made up of calcium dipicolinate. Calcium dipicolinate provides much resistance to spore under unfavorable conditions.

Unfavorable conditions trigger the bacteria to produce endospore. In this conditions, bacteria synthesize the large amounts of small acid soluble proteins (SASP) they bind to the vegetative bacterial B-form of DNA and convert it to A-form of DNA. The A-form DNA is shorter and wider form of DNA and shows more resistant to the DNA damage. When conditions are favorable to bacteria the peptidoglycan of cortex destroyed and releases the calcium dipicolinate. These conditions allow the bacteria to synthesize the DNA, RNA, and proteins. The formation of spores protects the bacteria from unfavorable conditions.

The bacterial endospores produced only by the gram-positive bacteria, not by the gram-negative bacteria. The making of spores by gram-positive bacteria under unfavorable conditions making them to survive in harsh environmental conditions and it is a selective advantage over gram-negative bacteria.

Endospore staining also called Schaeffer–Fulton staining. The primary stain used is malachite green and counterstain or secondary stain is Safranin. After staining of bacterial smears on the slide with these two stains the endospores appear as green under pink color background.