Question

Which of the following options is correct?
(a)Heterocyst are thin-walled and help in nitrogen fixation
(b) Archaebacteria are the oldest living
(c)Fossil cell wall of Archaebacteria and eubacteria are different but cell membrane are similar
(d)Penicillin is effective against mycoplasma

Answer 1

Hint: Archaea constitute a domain of single-celled organisms. Eubacteria, or true bacteria, are single-celled prokaryotic microorganisms. Penicillin is a group of antibiotics, derived originally from common moulds.

Complete answer:
Archaebacteria are the oldest living organisms. They can be found in some of the extreme environments. They are also known as extremophiles. Traces of Archaebacteria have been seen in 3.8 billion-year-old fossils. Thus, they are claimed as the oldest living organism. A heterocyst is a differentiated cyanobacterial cell that carries out nitrogen fixation. The heterocysts function as the sites for nitrogen fixation under aerobic conditions. They are found in Nitrogen deprived cells of bacteria like cyanobacteria, Anabaena, Nostoc, etc. Heterocyst synthesizes additional 3 layers of the cell wall, in turn, producing a thick cell wall. The cell wall and cell membrane of archaebacteria both differ from that of eubacteria. The antibiotic, penicillin is ineffective against mycoplasma.

Additional information:
-Archaea, any of a group of single-celled prokaryotic organisms that have distinct molecular characteristics separating them from bacteria as well as from eukaryotes like plants, animals, etc.
-Heterocysts are found in many species of filamentous blue‐green algae. They fix nitrogen from dinitrogen in the air using the enzyme nitrogenase, in order to provide the cells in the filament with nitrogen for biosynthesis. Nitrogenase is inactivated by oxygen, so the heterocyst must create a micro-anaerobic environment.
-Penicillin is a group of antibiotics, derived originally from common moulds known as Penicillium moulds. Penicillin is given to patients with an infection caused by bacteria.

Note:
-Some types of bacterial infections that may be treated with penicillin include pneumonia, strep throat, meningitis, syphilis, and gonorrhea, etc.
-Penicillin is effective only against Gram-positive bacteria. So it is not effective against Gram-negative bacteria.
-This is because Gram-negative bacteria have a lipopolysaccharide and protein layer that surrounds the peptidoglycan layer of the cell wall. This prevents the penicillin from attacking.