Lack of mycothiol and ergothioneine induces different protective mechanisms in Mycobacterium smegmatis

Abstract

Mycobacterium smegmatis contains the low molecular weight thiols, mycothiol (MSH) and ergothioneine (ESH). Examination of transposon mutants disrupted in mshC and egtA, involved in the biosynthesis of MSH and ESH respectively, demonstrated that both mutants were sensitive to oxidative, alkylating, and metal stress. However, the mshC mutant exhibited significantly more protein carbonylation and lipid peroxidation than wildtype, while the egtA mutant had less protein and lipid damage than wildtype. We further show that Ohr, KatN, and AhpC, involved in protection against oxidative stress, are upregulated in the egtA mutant. In the mshC mutant, an Usp and a putative thiol peroxidase are upregulated. In addition, mutants lacking MSH also contained higher levels of Coenzyme F420 as compared to wildtype and two Coenzyme F420 dependent enzymes were found to be upregulated. These results indicate that lack of MSH and ESH result in induction of different mechanisms for protecting against oxidative stress.

The proteobacterial species Burkholderia pseudomallei produces ergothioneine, which enhances virulence in mammalian infection

“…This could reflect the predominant role of GSH in this gram-negative genus because we found that GSH is indeed made in much higher quantities than EGT is under all conditions tested. Furthermore, we do not see crosstalk between the EGT and GSH pathways in Burkholderia species, unlike that found in Mycobacterium species, in which a mycothiol mutant showed significantly increased EGT production, and mycothiol and EGT are both shown to be important for protection against oxidative stress (7,8). Burkholderia species are predominantly saprophytic organisms, and in a way, their lifestyles could be more closely related to fungi than to mycobacteria.…”

Role of Ergothioneine in Microbial Physiology and Pathogenesis

“…7 ). The sensitivity to all of these agents was reversed in the complemented strain demonstrating the importance of EGT in M. smegmatis ( 61 ).…”

“…Singh et al reported that the transposon mutant of egtA in M. smegmatis did not produce EGT; however, there is no difference in growth compared with the wild type ( 61 ). The egtA mutant, R119, was shown to be highly susceptible to oxidative agents such as cumene hydroperoxide and diamide; alkylating agents such as N-ethylmalemide, iodoacetamide, and chlorodinitrobenzene; and metals such as Cd 2+ , Cu 2+ , SeO 3 2− , TeO 3 2− , and CrO 4 2− ( Fig.…”

“…Peroxidase activity in the EGT mutant was assessed to determine if EGT acts as an electron donor to peroxidase(s) by measuring the decomposition of H 2 O 2 , cumene hydroperoxide, and tert -butyl hydroperoxide ( 61 ). The amount of peroxides in the EGT mutant were the same as that in wild type, showing that EGT is not involved directly in the reduction of peroxides in M. smegmatis or another mechanism that detoxifies the peroxides is induced in the EGT mutant, such as Ohr, KatG, or AhpC ( 61 ). However, these experiments do not rule out the presence of an EGT-dependent peroxidase activity in M. smegmatis .…”

“…Sao Emani et al ( 54 ) showed that an M. smegmatis mutant lacking egtD was unable to synthesize EGT and they also demonstrated that EGT protects M. smegmatis against peroxides such as tert -butyl hydroperoxide and cumene hydroperoxide ( 54 ). The M. smegmatis egtD mutant was more susceptible to the lipid peroxides, cumene peroxide and tert-butyl hydroperoxide, in contrast to the M. smegmatis egtA mutant, which was only sensitive to cumene peroxide ( 61 ). Greater susceptibility to cumene hydroperoxide, hydrogen peroxide, and paraquat was also observed in an Mtb egtD transposon mutant than in an Mtb egtA transposon mutant ( 52 ).…”