Transcriptional Profiling Identifies the Metabolic Phenotype of Gonococcal Biofilms

Abstract

Neisseria gonorrhoeae, the etiologic agent of gonorrhea, is frequently asymptomatic in women, often leading to chronic infections. One factor contributing to this may be biofilm formation. N. gonorrhoeae can form biofilms on glass and plastic surfaces. There is also evidence that biofilm formation may occur during natural cervical infection. To further study the mechanism of gonococcal biofilm formation, we compared transcriptional profiles of N. gonorrhoeae biofilms to planktonic profiles. Biofilm RNA was extracted from N. gonorrhoeae 1291 grown for 48 h in continuous-flow chambers over glass. Planktonic RNA was extracted from the biofilm runoff. In comparing biofilm with planktonic growth, 3.8% of the genome was differentially regulated. Genes that were highly upregulated in biofilms included aniA, norB, and ccp. These genes encode enzymes that are central to anaerobic respiratory metabolism and stress tolerance. Downregulated genes included members of the nuo gene cluster, which encodes the proton-translocating NADH dehydrogenase. Furthermore, it was observed that aniA, ccp, and norB insertional mutants were attenuated for biofilm formation on glass and transformed human cervical epithelial cells. These data suggest that biofilm formation by the gonococcus may represent a response that is linked to the control of nitric oxide steady-state levels during infection of cervical epithelial cells.

Characterization of an ntrX Mutant of Neisseria gonorrhoeae Reveals a Response Regulator That Controls Expression of Respiratory Enzymes in Oxidase-Positive Proteobacteria

“…The N. gonorrhoeae 1291 wild-type strain and the Ng-ntrX isogenic mutant were transformed with plasmid pCmGFP, encoding a green fluorescent protein (GFP) (39). Formation and analyses of biofilms were performed as described previously (38,40), with the exception that cells were grown under the same aerobic conditions described for the microarray analysis, prior to their inoculation into biofilm growth chambers. The colonies used to inoculate cultures for biofilm assays were assessed for morphology to ensure equivalent levels of piliation as described previously (41).…”

“…The colonies used to inoculate cultures for biofilm assays were assessed for morphology to ensure equivalent levels of piliation as described previously (41). The biofilm images are three-dimensional reconstructions of stacked z-series taken at ϫ200 magnification and were rendered by Volocity (Improvision, Inc., Lexington, MA) as described previously (40).…”

Identification of Genes Involved in Neisseria meningitidis Colonization

“…More recently, it has been evidenced that wild-type (WT) encapsulated N. meningitidis was able to form biofilms on human tissue culture cells in a flow chamber (8). In addition, proteomic and transcriptomic studies comparing planktonic versus biofilm grown meningococcus or gonococcus over inert surface have highlighted the role of enzymes involved in denitrification and adaptation to reactive oxygen species (13)(14)(15).…”

Phenotypic Characterization of acopAMutant of Neisseria gonorrhoeae Identifies a Link between Copper and Nitrosative Stress

“…The gonococcus itself generates NO, as it possesses a nitrite reductase (AniA) which converts nitrite (NO 2 Ϫ ) to NO under microaerobic conditions (13). An NO reductase (NorB) further catalyzes the conversion of NO to nitrous oxide (N 2 O) via an energy-conserving respiratory process (10), and notably, formation of a gonococcal biofilm on cervical epithelial cells requires both AniA and NorB (5).…”