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The capsular polysaccharide synthesis (cps) locus of Neisseria meningitidis is implicated in invasive meningococcal disease. The synthesis (synABCD) and transport (ctrABCD) operons are transcribed in opposite directions from a common intergenic region, and the expression is negatively regulated by the bacterial two-component system (TCS) misR/misS and thermosensitive RNA folding. However, these mechanisms do not fully explain the stationary phase responses, and the cis-acting elements remain to be fully characterized. Using the GFP reporter gene and site-directed mutagenesis, cis-regulatory elements in the 134 bp intergenic region, NmIR, were investigated. While confirming a known RpoD promoter, an additional potential promoter element and putative binding sites for the transcription factors fis and lexA were identified through sequence analysis. Deletion of the putative lexA binding site led to an increase in GFP fluorescence. The N. meningitidis genome carries only one lexA homolog, the helix-turn-helix regulator XRE family member (GenBank-NMB0910, HTH_XRE). Trans-complementation of the NmIR-GFP reporter with the N. meningitidis HTH_XRE expression plasmid led to increased fluorescence. Trans-complementation with either misR/misS or nusG decreased reporter gene expression. Consistent with previous reports, deletion of the RpoD promoter reduced expression by 50%, suggesting the redundancy of promoter elements in the intergenic region. Thus, the results confirm the functioning of an exogenous N. meningitidis capsule synthesis promoter in Escherichia coli and demonstrate its regulation through trans-complementation by misR/misS, HTH_XRE, and nusG. 

ABSTRACT Mucins are glycoproteins which can be found in host cell membranes and as a gelatinous surface formed from secreted mucins. Mucosal surfaces in mammals form a barrier to invasive microbes, particularly bacteria, but are a point of attachment for others.Clostridioides difficileis an anaerobic bacterium, which colonizes the mammalian gastrointestinal (GI) tract and is a common cause of acute GI inflammation leading to a variety of negative outcomes. AlthoughC. difficiletoxicity stems from secreted toxins, colonization is a prerequisite forC. difficiledisease. WhileC. difficileis known to associate with the mucous layer and underlying epithelium, the mechanisms underlying these interactions that facilitate colonization are less well understood. To understand the molecular mechanisms by whichC. difficileinteracts with mucins, we usedex vivomucosal surfaces to test the ability ofC. difficileto bind to mucins from different mammalian tissues. We found significant differences inC. difficileadhesion based upon the source of mucins, with highest levels of binding observed to mucins purified from the human colonic adenocarcinoma line LS174T and lowest levels of binding to porcine gastric mucin. We also observed defects in adhesion by mutants deficient in flagella but not type IV pili. These results imply that interactions between host mucins andC. difficileflagella facilitate the initial host attachment ofC. difficileto host cells and secreted mucus. IMPORTANCEClostridioides difficileis one of the leading causes of hospital-acquired infections worldwide and presents challenges in treatment due to recurrent gastrointestinal disease after treatment with antimicrobials. The mechanisms by whichC. difficilecolonizes the gut represent a key gap in knowledge, including its association with host cells and mucosa. Our results show the importance of flagellin for specific adhesion to mucosal hydrogels and can help to explain prior observations of adhesive defects in flagellin and pilin mutants. 

Acinetobacterinfections are a growing burden on health care systems worldwide due to increasing antimicrobial resistance through multiple mechanisms. Biofilm formation is an established mechanism of antimicrobial resistance, and its inhibition has the potential to potentiate the use of existing drugs against pathogenicAcinetobacter. 

ABSTRACT Buruli ulcer disease is a neglected tropical disease caused by the environmental pathogen Mycobacterium ulcerans . The M. ulcerans major virulence factor is mycolactone, a lipid cytotoxic compound whose genes are carried on a plasmid. Although an exact reservoir and mode(s) of transmission are unknown, data provide evidence of both. First, Buruli ulcer incidence and M. ulcerans presence have been linked to slow-moving water with low oxygen. M. ulcerans has also been suggested to be sensitive to UV due to termination in crtI , encoding a phytoene dehydrogenase, required for carotenoid production. Further, M. ulcerans has been shown to cause disease following puncture but not when introduced to open abrasion sites, suggesting that puncture is necessary for transmission and pathology. Despite these findings, the function and modulation of mycolactone and other genes in response to dynamic abiotic conditions such as UV, temperature, and oxygen have not been shown. In this study, we investigated modulation of mycolactone and other genes on exposure to changing UV and oxygen microenvironmental conditions. Mycolactone expression was downregulated on exposure to the single stress high temperature and did not change significantly with exposure to UV; however, it was upregulated when exposed to microaerophilic conditions. Mycolactone expression was downregulated under combined stresses of high temperature and low oxygen, but there was upregulation of several stress response genes. Taken together, results suggest that temperature shapes M. ulcerans metabolic response more so than UV exposure or oxygen requirements. These data help to define the environmental niche of M. ulcerans and metabolic responses during initial human infection. IMPORTANCE Buruli ulcer is a debilitating skin disease caused by the environmental pathogen Mycobacterium ulcerans . M. ulcerans produces a toxic compound, mycolactone, which leads to tissue necrosis and ulceration. Barriers to preventing Buruli ulcer include an incomplete understanding of M. ulcerans reservoirs, how the pathogen is transmitted, and under what circumstances mycolactone and other M. ulcerans genes are expressed and produced in its natural environment and in the host. We conducted a study to investigate M. ulcerans gene expression under several individual or combined abiotic conditions. Our data showed that mycolactone expression was downregulated under combined stresses of high temperature and low oxygen but there was upregulation of several stress response genes. These data are among only a few studies measuring modulation of mycolactone and other M. ulcerans genes that could be involved in pathogen fitness in its natural environment and virulence while within the host.