Cobalamin is present in cells of non-tuberculous mycobacteria, but not in Mycobacterium tuberculosis

Abstract

Cobalamin (vitamin B12) is a structurally complex molecule that acts as a cofactor for enzymes and regulates gene expression through so-called riboswitches. The existing literature on the vitamin B12 synthesis capacity in Mycobacterium tuberculosis is ambiguous, while in non-tuberculous mycobacteria (NTM) is rather marginal. Here we present the results of our investigation into the occurrence of vitamin B12 in mycobacteria. For detection purposes, immunoassay methods were applied to cell lysates of NTM and M. tuberculosis clinical and laboratory strains grown under different conditions. We show that whereas vitamin B12 is present in cells of various NTM species, it cannot be evidenced in strains of differently cultured M. tuberculosis, even though the genes responsible for vitamin B12 synthesis are actively expressed based on RNA-Seq data. In summary, we conclude that the production of vitamin B12 does occur in mycobacteria, with the likely exception of M. tuberculosis. Our results provide direct evidence of vitamin B12 synthesis in a clinically important group of bacteria.

In Silico Exploration of Mycobacterium tuberculosis Metabolic Networks Shows Host-Associated Convergent Fluxomic Phenotypes

“…All the members of A1, A3 and A4 are affected by different potentially deleterious SNPs in this gene. HemB protein participates in an early step of the synthesis of cobalamin and mycobactins, among other compounds [34,[62][63][64]. Cobalamin is a cofactor of many enzymes and regulates gene expression [34].…”

“…HemB protein participates in an early step of the synthesis of cobalamin and mycobactins, among other compounds [34,[62][63][64]. Cobalamin is a cofactor of many enzymes and regulates gene expression [34]. Mycobactins are small molecules that sequester iron ions from ferritin, transferrin, lactoferrin and hemoglobin, the major sources of iron within the host's cells [64][65][66].…”

“…This gene has a single mutation in lineages A2, A3 and A4, probably appearing in their common ancestor in a single event. The other is Rv0512 (hemB), which codes for delta-aminolevulinic acid dehydratase, involved in the synthesis of cobalamin, a cofactor of many enzymes [34]. This gene has three different non-synonymous SNPs restricted to three out of four animal-associated lineages (Figure 2).…”

Mycobacterium tuberculosisemploys atypical and different classes of B12switches to control separate operons

“…Adenosylcobalamin (AdoB 12 ), methylcobalamin (MeB 12 ), and hydroxocobalamin (HyB 12 ) are naturally occurring B 12 isoforms, whereas cyanocobalamin (CNB 12 ) is predominantly produced in large scale as a derivative of the natural B 12 isoforms in Pseudomonas denitrificans, Propionibacterium shermanii, or Sinorhizobium meliloti (37). Mycobacterium tuberculosis, the aetiological agent of tuberculosis (38,39), lacks the ability to synthesise B 12 (40,41) due to the deletion of cobF, encoding a precorrin-6A synthase involved in the de novo B 12 biosynthesis pathway, which is otherwise intact (42)(43)(44). Still, M. tuberculosis encodes several B 12 -dependent enzymes, suggesting that the pathogen utilises host-derived B 12 whenever available (45,46), although these enzymes are found alongside alternative B 12 -independent counterparts for the same metabolic processes.…”

>b<Host adaptation of >i<Mycobacterium tuberculosis>/i< and >i<Mycobacterium bovis>/i<:>/b< a genomic and transcriptional approach

“…Cobalamin is not provided in the 7H9-OADC-Pyr-Tween medium, and the uptake (lower bound) was set to zero. The functional existence of a de novo pathway for vitamin B12 in M. tuberculosis is controversial, and a recent study could not detect vitamin B12 in M. tuberculosis grown in various conditions in vitro (MINIAS et al, 2021). If we consider that M. bovis lacks the ability to generate vitamin B12, the MMC is probably incorrectly developed in the GSM, suggesting that the formation of succinyl-CoA by this direction is unlikely.…”