Question

You visit a small island, which just two days earlier experienced a volcanic explosion. Nothing appears to be alive on the island, but you collect soil samples and place them on culture media in the laboratory, Within 24 hours you find actively growing bacterial colonies on several of you plates. The bacteria that you find are most likely to

A. have sex pili

B. have a glycocalyx

C. have endospores

D. have capsules

Answer 1

Q) You visit a small island, which just two days earlier experienced a volcanic explosion. Nothing appears to be alive on the island, but you collect soil samples and place them on culture media in the laboratory, Within 24 hours you find actively growing bacterial colonies on several of you plates. The bacteria that you find are most likely to

A. have sex pili B. have a glycocalyx C. have endospores D. have capsules

Ans) have endospores

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 found in soil and water, where they may survive for long periods of time and the formation of endospore is a differentiation event of bacteria that allow the bacteria to survive harsh environmental conditions. They are highly resistant to environmental conditions like high temperature (some bacteria retain viability after several hours of boiling), irradiation, strong acids, disinfectants, extreme pH, antibiotics, UV, lyzozyme and they are most durable cell structures produced in nature. They are produced by gram positive bacteria under unfavorable conditions during late log phase or early stationary phase by process called sporulation. The typical spore size is 0.2 µm.

Each endospore has four layers

1) Exosporium: it is the outer most layer of the spore which interacts with the environment or host organism and it contains the antigens. It is made up of the proteins and in some bacteria it made up polysaccharides and lipids. In B. anthracis and B.cereus Cot protein is observed in Exosporium.

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

3) Cortex: it is loosely attached layer which cover the core made up of peptidoglycan and give heat resistance and maintains spore dormancy.

4) Core: it is innermost layer of spore contains DNA, proteins and ribosomes and it is metabolically inactive portion of spore.