Table 2.

Functional roles of selected microbes in PCa

Microbe	Possible mechanism of action
Cutibacterium acnes	Induce secretion of cytokines and chemokines such as IL-6 and IL-8 [70, 71], activate transcription factors such as NF-κB and STAT3 [70], and induce production of reactive oxygen species [75], all leading to chronic inflammation and pre-cancerous transformation of the prostatic epithelia.
E.coli	Chronic inflammation and tissue damage mediated by CNF1 [81].
Faecalibacterium prausnitzii	Down-regulation of pro-inflammatory cytokines TNF-α, TNF-β and IL-6 [82], and increased production of anti-inflammatory cytokine IL-10 [83] in normal tissue.
Ruminococcus gnavus	Convert androgen precursors to active androgen enabling alternative source of androgens and resulting in treatment resistance and disease progression [84].