Impact of Moderate Temperature Changes on Neisseria meningitidis Adhesion Phenotypes and Proteome

Abstract

bNeisseria meningitidis, the meningococcus, bears the potential to cause life-threatening invasive diseases, but it usually colonizes the nasopharynx without causing any symptoms. Within the nasopharynx, Neisseria meningitidis must face temperature changes depending on the ambient air temperature. Indeed, the nasopharyngeal temperature can be substantially lower than 37°C, the temperature commonly used in experimental settings. Here, we compared the levels of meningococcal biofilm formation, autoaggregation, and cellular adherence at 32°C and 37°C and found a clear increase in all these phenotypes at 32°C suggestive of a stronger in vivo colonization capability at this temperature. A comparative proteome analysis approach revealed differential protein expression levels between 32°C and 37°C, predominantly affecting the bacterial envelope. A total of 375 proteins were detected. Use of database annotation or the PSORTb algorithm predicted 49 of those proteins to be localized in the outer membrane, 21 in either the inner or outer membrane, 35 in the periplasm, 56 in the inner membrane, and 208 in the cytosol; for 6 proteins, no annotation or prediction was available. Temperature-dependent regulation of protein expression was seen particularly in the periplasm as well as in the outer and inner membranes. Neisserial heparin binding antigen (NHBA), NMB1030, and adhesin complex protein (ACP) showed the strongest upregulation at 32°C and were partially responsible for the observed temperature-dependent phenotypes. Screening of different global regulators of Neisseria meningitidis suggested that the extracytoplasmic sigma factor E might be involved in temperature-dependent biofilm formation. In conclusion, subtle temperature changes trigger adaptation events promoting mucosal colonization by meningococci. Microorganisms constantly adapt to changing environmental conditions. These changes include oxygen and nutrient availability, osmotic conditions, and temperature. The physiology of bacterial adaptation, including the underlying regulatory mechanisms that operate in response to radical temperature changes such as classical heat shock or cold shock, has been studied intensely (1-3). The heat shock response occurs during a transient upshift of growth temperature from 37°C to approximately 50°C (4). The heat shock response is controlled by the alternative sigma factor 32 , which regulates the expression of heat shock proteins mainly involved in protein folding or processing (4). In Escherichia coli, the cold shock response is triggered by a transient downshift from 37°C to 10°C that leads to generally slower transcriptional and translational responses except for about 26 upregulated proteins (5). The functions of these so-called cold shock proteins are less well understood than those of heat shock proteins, but they are likely involved in securing proper transcription, translation, and protein folding (5). Surprisingly little is known about the influence on bacterial physiology of slight temperature differences within mamma...

Comparative Genome Sequencing Reveals Within-Host Genetic Changes in Neisseria meningitidis during Invasive Disease

“…Lipooligosaccharide (LPS) electrophoresis was used to compare the LPS pattern between throat and corresponding blood isolates and was carried out as described in [56]. Briefly, bacteria were grown over night on Columbia blood agar plates (bioMérieux).…”

“…After electrophoresis, gels were stained by silver staining as described in ref. [56] and photographed using a Bio-Rad ChemiDoc MP imaging system.…”

Neisseria Heparin Binding Antigen is targeted by the human alternative pathway C3-convertase

“…Recombinant NHBA-derived C2 fragment exerts a toxic effect on endothelial cells altering endothelial permeability [ 9 ]. The recent finding that NHBA protein is more expressed and cleaved at lower temperatures than 37°C [ 12 ], which are temperatures encountered during N . meningitidis initial colonization of the upper respiratory tract, led us to hypothesize that C2 fragment could also alter the epithelial permeability and facilitate the traversal of N .…”

“…Since NHBA expression is upregulated at 32°C [ 12 ], a temperature encountered during N . meningitidis initial colonization of the upper respiratory tract [ 13 ], we hypothesized that the C2 fragment could also alter the epithelial permeability and facilitate the traversal of N .…”

Emerging experience with meningococcal serogroup B protein vaccines

“…In the absence of the bacterial capsule, heparin binding mediated by NHBA is associated with increased survival of N. meningitidis in human serum and might facilitate adherence to host tissues by binding to heparan sulfate proteoglycans [35]. Recently, it has been found that NHBA expression is temperature dependent and higher at 30°C and 32°C, suggesting that NHBA might be up-regulated in the nasopharyngeal niche and be involved in the attachment to epithelial cells and colonization [81]. NHBA is recognized by sera from patients convalescing from IMD and induces SBA that correlates with the level of NHBA expression [35].…”