Erysipelatoclostridium ramosum

Bacterial Information	Value
Taxonomy level	Species
NCBI Taxonomy ID	1547
Alternative names	Clostridium ramosum
Phylum	Firmicutes
Family	Erysipelotrichaceae
Genus	Erysipelatoclostridium
Gram stain	Gram-positive
Oxygen requirements	Strictly anaerobic
Spore-forming	No
Motile	No
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Table of Contents

• Overview
• Biological information
  • Serotonin and obesogenic potential

Overview

Erysipelatoclostridium ramosum (or Clostridium ramosum) is an anaerobic, non-motile, thin, spore-forming, Gram-positive bacterium that is among the gut flora of humans. It is potentially obesogenic (Mandić 2019)(Woting 2014).

Biological information

Serotonin and obesogenic potential

After 4 weeks on a high-fat diet (HFD), mice mono-associated with C. ramosum (Cra mice) displayed increased serotonin levels in plasma, increased weight, and a reduction of plasma kynurenine compared to germ free (GF) mice (Mandić 2019). Increased intestinal serotonin availability was also observed compared to both GF mice and low-fat diet (LFD) Cra mice, indicating that even though C. ramosum alone increases serotonin, the effect on host serotonin is significantly enhanced with a high-fat diet.

C. ramosum lysates (and bacterial lysates to a lesser degree) were capable of increasing serotonin release from cultured chromaffin cells and colonic organoids (Mandić 2019). Microbial metabolites (especially from spore-forming bacteria) such as deoxycholate (a secondary bile acid converted from cholate) stimulate serotonin release from enterochromaffin cells (Mandić 2019)(Yano 2015).

Further, ileal and colonic levels of CD36, FATP4, PLIN2, and PPAR-α were increased in Cra mice compared to GF mice, indicating that C. ramosum promotes absorption of fatty acids in the intestine and that the process is triggered by PPAR-α activation (Mandić 2019). Serotonin was shown in cell cultures with HT-29 and Caco-2 cells to stimulate expression of major proteins involved in intestinal translocation of fatty acids. Therefore, the link between C. ramosum and obesity may be related to increased lipid absorption. Markers of lipolysis, β-oxidation and lipogenesis were reduced in HFD-fed Cra mice, contrary to reports that serotonin favours lipolysis as an adaptation to fasting (Sumara 2012).