How many bacteria are produced in four hours if a bacterium divides once in half an hour?

Which of the following includes microorganisms that lack a defined nucleus but contain genetic material (nucleoid)?

$S:$ Methanogens are responsible for the production of methane.
$R:$ They can survive even in acidic and high-temperature conditions.

Which of the following is included in the kingdom $Monera$?

$S$ - Statement: Bacteria are divided into two groups based on the staining procedure developed by Gram.
$R$ - Reason: Bacteria that take up the Gram stain are called Gram-negative.

Which of the following prokaryotes lacks a cell wall?