The habitat of $E. coli$ is

Which of the following groups exhibits the most extensive nutritional diversity?

The smallest living cells with a cell wall are:

Select the correct statements from the given statements $(1-4)$ regarding the characteristics of some organisms.
$(1)$ Methanogens are Archaebacteria that produce methane in marshy areas.
$(2)$ $Nostoc$ is a flagellated blue-green alga that fixes atmospheric nitrogen.
$(3)$ Chemosynthetic autotrophic bacteria synthesize cellulose from glucose.
$(4)$ Mycoplasma lacks a cell wall and can survive without oxygen.

Methanogens are most abundant in a

'Peptidoglycan' is a characteristic constituent of the cell wall of