Which bacteria are used in a gobar gas plant?

Which of the following is responsible for the production of biogas?

Assertion $(S)$: $H_2$ is capable of converting solar energy into chemical energy.
Reason $(R)$: Photosynthetic microorganisms produce $H_2$.

Which gas is produced in large amounts when bacteria act on cellulosic material in biogas production?

Methanogens,particularly $Methanobacterium$,grow anaerobically on cellulosic material and produce:
$I.$ Methane
$II.$ Carbon dioxide
$III.$ Oxygen
$IV.$ Ethane
Choose the correct option.

Which microorganisms are responsible for the production of gas in the biogas plant shown in the figure?