Cysteine Desulfurase IscS2 Plays a Role in Oxygen Resistance in Clostridium difficile

Abstract

is an anaerobic, spore-forming bacterium capable of colonizing the gastrointestinal tract of humans following disruption of the normal microbiota, typically from antibiotic therapy for an unrelated infection. With approximately 500,000 confirmed infections leading to 29,000 deaths per year in the United States, infection (CDI) is an urgent public health threat. We previously determined that survives in up to 3% oxygen. Low levels of oxygen are present in the intestinal tract, with the higher concentrations being associated with the epithelial cell surface. Additionally, antibiotic treatment, the greatest risk factor for CDI, increases the intestinal oxygen concentration. Therefore, we hypothesized that the genome encodes mechanisms for survival during oxidative stress. Previous data have shown that cysteine desulfurases involved in iron-sulfur cluster assembly are involved in protecting bacteria from oxidative stress. In this study, deletion of a putative cysteine desulfurase (630_12790/IscS2) involved in the iron-sulfur cluster (Isc) system caused a severe growth defect in the presence of 2% oxygen. Additionally, this mutant delayed colonization in a conventional mouse model of CDI and failed to colonize in a germfree model, which has higher intestinal oxygen levels. These data imply an undefined role for this cysteine desulfurase in protecting from low levels of oxygen in the gut.

How the Anaerobic Enteropathogen Clostridioides difficile Tolerates Low O 2 Tensions

“…Thus, C. difficile vegetative cells cope with O 2 tensions during the colonization process and, in such nonstrict anaerobic environments, the ability to tolerate small amounts of O 2 appears to be essential ( 55 ). Accordingly, both sigB and iscS2 mutants, affected in their ability to tolerate low O 2 tensions, have been shown to be impaired in colonization in axenic mice ( 16 , 17 ). Since both revRbrs and FDPs play a crucial role in C. difficile low O 2 tolerance, further studies are needed to show that these proteins are important during the colonization process.…”

“…While strictly anaerobic, C. difficile is able to grow in nonstrict anoxic conditions (1 to 3% O 2 ) ( 15 ), indicating that this bacterium encodes an arsenal of proteins involved in O 2 detoxification and protection against oxidative stress. Recently, the deletion of the iscS2 gene encoding a cysteine desulfurase likely involved in Fe-S cluster biogenesis was shown to cause a severe growth defect in the presence of 2% O 2 ( 16 ). Another essential actor in the C. difficile ability to tolerate low O 2 concentrations is the alternative sigma factor involved in the general stress response, σ B .…”

Acyl Carrier Protein 3 Is Involved in Oxidative Stress Response in Pseudomonas aeruginosa

“…It is interesting to note that the putative interaction between Acp3 and IscC mentioned above may also be related to oxidative stress. This is because a strain of C. difficile lacking IscS2 (the homologue of IscS) fails to grow when oxygen levels go above 2% ( Giordano et al, 2018 ) suggesting it protects against oxidative stress. However, it needs to be established whether binding of Acp3 to IscS represses its cysteine desulfurase activity similar to KatA, or whether it enhances activity.…”

Microbiota of MR1 deficient mice confer resistance against Clostridium difficile infection

“…Cd was administered by oral gavage as described above. The doses used to infect the mice were chosen as they have been previously shown to sufficiently cause Cd colonization [26, 39].…”