The cell wall of $Nostoc$ is made up of:

The difference between Gram-positive and Gram-negative bacteria is due to the:

The given figure shows the structure of filamentous blue-green algae,Nostoc,with a structure marked as $X$. Select the option which shows the correct identification of $X$ with its feature.

Peptidoglycan present in the bacterial cell envelope is:

Match the following columns:

Column-$I$	Column-$II$
$(A)$ Halophiles	$(I)$ Gram-negative bacteria
$(B)$ Thermoacidophiles	$(II)$ Inhabit extremely salty areas
$(C)$ Spirochaetes	$(III)$ Responsible for methane production
$(D)$ Firmicutes	$(IV)$ Survive in acidic and high-temperature conditions
	$(V)$ Gram-positive bacteria

Which of the following are called bacteria without cell wall?