The Fused Methionine Sulfoxide Reductase MsrAB Promotes Oxidative Stress Defense and Bacterial Virulence in Fusobacterium nucleatum

Camacho

et al. 2022

mBio

Fusobacterium nucleatum is a key commensal anaerobe of the human oral cavity that plays a significant role in oral biofilm development and contributes to additional pathologies at extraoral sites, such as promoting preterm birth and colorectal cancer. Although F. nucleatum is known as a major producer of hydrogen sulfide (H 2 S), its genetic determinants and physiological functions are not well understood.

Section: Resultssupporting

confidence: 93%

Genetic Determinants of Hydrogen Sulfide Biosynthesis in Fusobacterium nucleatum Are Required for Bacterial Fitness, Antibiotic Sensitivity, and Virulence

Camacho

et al. 2022

mBio

“…4A-B). An interesting example is activation of the dicistronic operon ccdA - msrAB , which is paralogues to an operon previously linked to the defense against hydrogen peroxide in F. nucleatum (Dataset S1) (13). Thus, the σ E regulon in F. nucleatum might serve a dual function by neutralizing oxygen and by modulating the bacterial envelope, acting in synergy in this anaerobe bacterium.…”

Section: Discussionmentioning

confidence: 99%

“…These might involve phosphorylation as shown for the Vibrio parahaemolyticus σ factor EcfP (27) or a TCS as seen during activation of SigE in Streptomyces coelicolor (28). Interestingly, the fusobacterial TCS ModRS was recently shown to be involved in the response to H 2 O 2 (13). However, ModRS is not activated by oxygen (Dataset S3).…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

New genetic tools enable dissection of a global stress response in the early-branching speciesFusobacterium nucleatum

Ponath

Zhu

Cosi

et al. 2022

Preprint

Fusobacterium nucleatum, long known as a common oral microbe, has recently garnered attention for its ability to colonize tissues and tumors elsewhere in the human body. Clinical and epidemiological research has now firmly established F. nucleatum as an oncomicrobe associated with several major cancer types. However, with the current research focus on host associations, little is known about gene regulation in F. nucleatum itself, including global stress response pathways that typically ensure the survival of bacteria outside their primary niche. This is due to the phylogenetic distance of Fusobacteriota to most model bacteria, their limited genetic tractability, and paucity of known gene functions. Here, we characterize a global transcriptional stress response network governed by the extracytoplasmic function sigma factor, σE. To this aim, we developed several new genetic tools for this anaerobic bacterium, including four different fluorescent marker proteins, inducible gene expression, scarless gene deletion, and transcriptional and translational reporter systems. Using these tools, we identified a σE response partly reminiscent of phylogenetically distant Proteobacteria but induced by exposure to oxygen. Although F. nucleatum lacks canonical RNA chaperones such as Hfq, we uncovered conservation of the non-coding arm of the σE response in form of the non-coding RNA FoxI. This regulatory small RNA (sRNA) acts as an mRNA repressor of several membrane proteins, thereby supporting the function of σE. In addition to the characterization of a global stress response in F. nucleatum, the genetic tools developed here will enable further discoveries and dissection of regulatory networks in this early-branching bacterium.

“…However, periplasmic or outer-membrane-associated methionine sulfoxide reductases have recently been shown to play a pivotal role in protecting various bacterial pathogens from exogenous oxidative stress. MsrA/B-related enzymes have been identified in Streptococcus pneumoniae , Neisseria sp., Helicobacter and Fusobacterium [ 7 , 8 , 9 , 10 , 11 ], and in all cases were fusion proteins containing both an MsrA and an MsrB domain, some of which were anchored to the cell membrane. In these pathogens, MsrAB fusion proteins are required for full virulence, with an absence of MsrAB reducing disease severity [ 8 , 9 , 12 ].…”

Section: Introductionmentioning

confidence: 99%

The Peptide Methionine Sulfoxide Reductase (MsrAB) of Haemophilus influenzae Repairs Oxidatively Damaged Outer Membrane and Periplasmic Proteins Involved in Nutrient Acquisition and Virulence

et al. 2022

Sulfoxide-damage repair mechanisms are emerging as essential for the virulence of bacterial pathogens, and in the human respiratory pathogen Haemophilus influenzae the periplasmic MsrAB peptide methionine sulfoxide reductase is necessary for resistance to reactive chlorine species such as hypochlorite. Additionally, this enzyme has a role in modulating the host immune response to infection. Here, we have analysed the enzymatic properties of MsrAB, which revealed that both domains of the protein are catalytically active, with the turnover number of the MsrA domain being 50% greater than that for the MsrB domain. MsrAB was active with small molecular sulfoxides as well as oxidised calmodulin, and maximal activity was observed at 30°C, a temperature close to that found in the natural niche of H. influenzae, the nasopharynx. Analyses of differential methionine oxidation identified 29 outer membrane and periplasmic proteins that are likely substrates for MsrAB. These included the LldD lactate dehydrogenase and the lipoprotein eP4 that is involved in NAD and hemin metabolism in H. influenzae. Subsequent experiments showed that H. influenzae MsrAB can repair oxidative damage to methionines in purified eP4 with up to 100% efficiency. Our work links MsrAB to the maintenance of different adhesins and essential metabolic processes in the H. influenzae, such as NAD metabolism and access to L-lactate, which is a key growth substrate for H. influenzae during infection.