For each of the following describe and explain unique cellul

For each of the following, describe and explain unique cellular features that allow the cells to survive or withstand the indicated harsh condition.

A. Endospores - to survive boiling water

B. Gram negative cells - to survive exposure to large antibiotics like Vancomycin

C. Mycobacteria - to resist decolorization by acidified ethanol

D. Persister cells - to surive nutrient depletion for many months

Solution

A. Microorganisms during unfavorable environmental conditions such as nutrients are exhausted lead formation of a protective sheath in the form of endospore. The endospore formation is more prominent among gram positive bacteria having low G+C content. Due to outer proteinaceous coat of an endospore, the spore provide chemical and enzymatic resilence. The outer coat is followed by a thick specialized peptidoglycan layer known as cortex that helps to provide resistance to the endospore to higher temperatures (100⁰C).

B. Since bacteria can be classified as as Gram-positive or Gram-negative based on results of Gram stain. Gram-positive bacteria take up basic stain as they have a thick (25 nm) cell wall and Gram-negative bacteria (possess thinner (3 nm) cell wall and a second outer membrane. Vancomycin has large size and a complex structure which make it impermeable to cross the outer membrane of gram-negative organisms.

C. Ziel-Neelsen staining is used for Mycobacteria (M.tuberculosis) and it resists to release basic stain of Z-N stain(carbol-fuchsin ) upon treatment with acidified alcohol, so they appear as red rods against blue background, and are called as acid-fast bacteria. This property of acid alcohol resistance is due to the presence of specialized cell wall glycolipids known as mycolic acid.

D. Persister cells are those cells which are dormant forms of regular microbial cells that are tolerant to antibiotics. TisB toxin is a membrane bound protein in persister cells responsible for dorminant formation of cells and inturn antibiotic tolerance.