Growth Phase- and Nutrient Limitation-Associated Transcript Abundance Regulation inBordetella pertussis

Abstract

To survive in a host environment, microbial pathogens must sense local conditions, including nutrient availability, and adjust their growth state and virulence functions accordingly. No comprehensive investigation of growth phase-related gene regulation in Bordetella pertussis has been reported previously. We characterized changes in genome-wide transcript abundance of B. pertussis as a function of growth phase and availability of glutamate, a key nutrient for this organism. Using a Bordetella DNA microarray, we discovered significant changes in transcript abundance for 861 array elements during the transition from log phase to stationary phase, including declining transcript levels of many virulence factor genes. The responses to glutamate depletion exhibited similarities to the responses induced by exit from log phase, including decreased virulence factor transcript levels. However, only 23% of array elements that showed at least a fourfold growth phaseassociated difference in transcript abundance also exhibited glutamate depletion-associated changes, suggesting that nutrient limitation may be one of several interacting factors affecting gene regulation during stationary phase. Transcript abundance patterns of a Bvg ؉ phase-locked mutant revealed that the BvgAS two-component regulatory system is a key determinant of growth phase-and nutrient limitation-related transcriptional control. Several adhesin genes exhibited lower transcript abundance during stationary phase and under glutamate restriction conditions. The predicted bacterial phenotype was confirmed: adherence to bronchoepithelial cells decreased 3.3-and 4.4-fold at stationary phase and with glutamate deprivation, respectively. Growth phase and nutrient availability may serve as cues by which B. pertussis regulates virulence according to the stage of infection or the location within the human airway.During the course of infection, bacterial pathogens encounter a variety of challenging conditions in the host, including scarcity of carbon, nitrogen, iron, and other nutrients; fluctuations in pH; oxidative stress; and adverse conditions produced by the host innate and adaptive immune responses. In order to succeed, microorganisms must be able to modify their physiological state and virulence phenotype in accordance with changing features within the host, in a reciprocal and dynamic fashion. Growth phase-associated regulation is inherently related to pathogenicity, for in order to survive, bacteria must alter their growth rate and metabolic activity appropriately, according to cues in the host environment. Entry into stationary phase, defined as the moment when the bacterial growth rate begins to decline, is accompanied by development of cross-resistance to multiple stressors, promoting survival (34). In addition, studies have identified correlations between bacterial virulence and growth phase (22,38).No comprehensive study of growth phase-associated regulation has been performed with the obligate human pathogen Bordetella pertussis, the causative agent of...

Glutamate Limitation, BvgAS Activation, and (p)ppGpp Regulate the Expression of the Bordetella pertussis Type 3 Secretion System

“…The effect of glutamate limitation on gene expression in B. pertussis first was investigated by DNA microarray analysis (34). Contrary to the case in the present study, the amount of T3SS transcripts was decreased under glutamate limitation.…”

“…Contrary to the case in the present study, the amount of T3SS transcripts was decreased under glutamate limitation. Moreover, decreased transcript levels were observed during the transition from exponential to stationary phase (34). It is notable that Nicholson et al demonstrated that B. bronchiseptica expressed higher levels of T3SS genes and cytotoxicity mediated by T3SS in late exponential phase and stationary phase than during mid-exponential phase (35).…”

Meningococcal Internalization into Human Endothelial and Epithelial Cells Is Triggered by the Influx of Extracellular l -Glutamate via GltT l -Glutamate ABC Transporter in Neisseria meningitidis

“…For example, the expression of numerous pathogenic genes including SPI-1 in Salmonella enterica serovar Typhimurium is activated by an ArcAB-TolC efflux pump (63), and the transcription of T3SS in Pseudomonas aeruginosa is inhibited by the magnesium transporter MgtE (1). It is also known that the influx of environmental small molecules is linked to bacterial pathogenesis; the internalization of N. gonorrhoeae into human cells is inhibited by the influx of phosphate via the gonococcal major outer membrane porin PorB of serotype A (P.IA) (22,55), and transcript levels of many virulence genes in Bordetella pertussis are reduced under L-gluta- ϩ -gltM ϩ strain(HT1125), ⌬gltT-⌬gltM mutant (HT1414), the ⌬gltT-⌬gltM mutant in which gltT ϩ -gltM ϩ genes were ectopically complemented (HT1428), the gltT(Am) mutant (HT1452), the gltM(Oc) mutant (HT1453), and the derivatives of additional complementation of the popc-gltM ϩ gene at the iga locus of the above mutants (HT1539, HT1533, and HT1538) ( mate-depleted conditions (29). The transcription of T3SS in P. aeruginosa is also induced under a low-Ca 2ϩ environment by the elevation of cyclic AMP (cAMP), which induces transcription in cooperation with Vfr, a functional homologue of the E. coli cAMP receptor protein (64).…”

Conformational Changes of an Interdomain Linker Mediate Mechanical Signal Transmission in Sensor Kinase BvgS

“…In the laboratory, the bacteria shift to the avirulent Bvg Ϫ phase in response to the perception by BvgS of modulators such as MgSO 4 or nicotinate, at low temperatures, or under conditions of nutrient restriction (9)(10)(11)(12). We have shown, using a Phos-tag assay, that addition of nicotinate to the bacteria causes the dephosphorylation of BvgA much faster than if the reaction occurs spontaneously (12).…”