Characterization of the Haemophilus influenzae tehB gene and its role in virulence

Abstract

The Haemophilus influenzae ORF designated HI1275 in the Rd KW20 genomic sequence encodes a putative S-adenosyl methyltransferase with significant similarity to tellurite-resistance determinants (tehB) in other species. While the H. influenzae tehB can complement an Escherichia coli tehB mutation, thus restoring tellurite resistance, its role in H. influenzae is unknown. In a previous study defining the iron and haem modulon of H. influenzae, we showed that transcription of this gene in H. influenzae Rd KW20 increases during growth in iron-and haem-restricted media. Since iron and haem uptake genes, and other known virulence factors, constitute the majority of the iron-and haem-regulated gene set, we postulated that tehB may play a role in nutrient acquisition and/or the virulence of H. influenzae. A tehB mutant was constructed in the H. influenzae type b strain 10810 and was evaluated for growth defects in various supplemented media, as well as for its ability to cause infection in rat models of infection. Deletion of tehB leads to an increase in sensitivity both to tellurite and to the oxidizing agents cumene hydroperoxide, tert-butyl hydroperoxide and hydrogen peroxide. The tehB mutant additionally showed a significantly reduced ability to utilize free haem as well as several haem-containing moieties including haem-human serum albumin, haemoglobin and haemoglobin-haptoglobin. Examination of the regulation kinetics indicated that transcription of tehB was independent of both tellurite exposure and oxidative stress. Paired comparisons of the tehB mutant and the wild-type H. influenzae strain 10810 showed that tehB is required for wild-type levels of infection in rat models of H. influenzae invasive disease. To our knowledge this is the first report of a role for tehB in virulence in any bacterial species. These data demonstrate that H. influenzae tehB plays a role in both resistance to oxidative damage and haem uptake/utilization, protects H. influenzae from tellurite exposure, and is important for virulence of this organism in an animal model of invasive disease.

Corynebacterium diphtheriae putative tellurite-resistance protein (CDCE8392_0813) contributes to the intracellular survival in human epithelial cells and lethality of Caenorhabditis elegans

“…This mutant exhibited increased sensitivity to tellurite. Similar results were observed with a Haemophilus influenzae mutant for teh B ( Whitby et al 2010 ).…”

“…However, TeO 3 2- resistance is likely mediated via resistance to oxidative damage rather than the detoxification of the metal oxide itself ( Toptchieva et al 2003 , Chasteen et al. 2009 , Whitby et al 2010 ). Due to this, the CDCE83912_0813 mutant was further examined to determine its resistance to H 2 O 2 .…”

Haemophilus influenzae OxyR: Characterization of Its Regulation, Regulon and Role in Fitness

“…Previously, significant differences in the impact of numerous mutations on virulence when comparing 5-day old to 30 day-old rats have been reported [6], [7], [26]–[28]. When two groups of 30-day old rats were infected with either the wild-type or the mutant strain, the group infected with the oxyR mutant had consistently lower bacterial titers than the group infected with the wild-type strain (Fig.…”

The NsrR regulon in nitrosative stress resistance of Salmonella enterica serovar Typhimurium

“…6). STM1808 and YeaR are homologues of the Haemophilus influenzae TehB protein, which has been shown to be important for tellurite and oxidative stress resistance, and virulence in rats (Whitby et al ., 2010). H. influenzae TehB is bipartite in structure with an N‐terminal domain of unknown function (DUF1971) and a conserved C‐terminal AdoMet_MTase domain that functions as an S ‐adenosyl‐ l ‐methionine (SAM)‐dependent methyltransferase.…”