Q.32

Which of the following statement(s) is/are CORRECT about ‘stringent response’ in

bacteria?

(A) It is linked to reduced growth rate

(B) Guanosine tetraphosphate (ppGpp) alone is sufficient to trigger the process

(C) Both guanosine tetraphosphate (ppGpp) and guanosine pentaphosphate (pppGpp) are

required to trigger the process

(D) RelA and/or SpoT are/is involved in triggering the process

Stringent Response in Bacteria: Correct Statements Explained

The stringent response is a key stress adaptation mechanism in bacteria triggered by nutrient limitation. Correct options are A, B, and D, as they accurately describe its link to growth reduction, ppGpp sufficiency, and RelA/SpoT involvement.

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Reduced Growth Rate Link

Stringent response directly correlates with slowed bacterial growth during nutrient downshift. It halts processes like rRNA synthesis, replication, and translation to promote survival in famine conditions. Bacteria enter a dormant state, reducing metabolic activity and fitness costs.

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ppGpp Trigger Role

Guanosine tetraphosphate (ppGpp) alone suffices to initiate stringent response by accumulating as an alarmone under stress. While pppGpp also forms, ppGpp drives core reprogramming of transcription and metabolism. This makes option B correct and C incorrect, as both are not strictly required.

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RelA and SpoT Function

RelA synthesizes (p)ppGpp during amino acid starvation, while SpoT handles other stresses like carbon or fatty acid limitation and also degrades it. Mutants lacking these show defective response and prolonged growth lags. Thus, option D holds true.

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Option Analysis Table