Glucose uptake in Azotobacter vinelandii occurs through a GluP transporter that is under the control of the CbrA/CbrB and Hfq-Crc systems

Abstract

Azotobacter vinelandii, a strict aerobic, nitrogen fixing bacterium in the Pseudomonadaceae family, exhibits a preferential use of acetate over glucose as a carbon source. In this study, we show that GluP (Avin04150), annotated as an H+-coupled glucose-galactose symporter, is the glucose transporter in A. vinelandii. This protein, which is widely distributed in bacteria and archaea, is uncommon in Pseudomonas species. We found that expression of gluP was under catabolite repression control thorugh the CbrA/CbrB and Crc/Hfq regulatory systems, which were functionally conserved between A. vinelandii and Pseudomonas species. While the histidine kinase CbrA was essential for glucose utilization, over-expression of the Crc protein arrested cell growth when glucose was the sole carbon source. Crc and Hfq proteins from either A. vinelandii or P. putida could form a stable complex with an RNA A-rich Hfq-binding motif present in the leader region of gluP mRNA. Moreover, in P. putida, the gluP A-rich Hfq-binding motif was functional and promoted translational inhibition of a lacZ reporter gene. The fact that gluP is not widely distributed in the Pseudomonas genus but is under control of the CbrA/CbrB and Crc/Hfq systems demonstrates the relevance of these systems in regulating metabolism in the Pseudomonadaceae family.

Characterization of the CrbS/R Two-Component System in Pseudomonas fluorescens Reveals a New Set of Genes under Its Control and a DNA Motif Required for CrbR-Mediated Transcriptional Activation

“…CbrA is a histidine kinase that functions as a global regulator of metabolism, virulence, and antibiotic resistance in the Pseudomonadaceae (Nishijyo et al, 2001 ; Zhang and Rainey, 2007 ; Yeung et al, 2011 , 2014 ; Quiroz-Rocha et al, 2017 ). Its cognate response regulator, CbrB, possesses a σ54-interacting domain, which regulates expression of different metabolic genes.…”

“…Its cognate response regulator, CbrB, possesses a σ54-interacting domain, which regulates expression of different metabolic genes. For example, the CbrAB system governs the utilization of histidine and other amino acids in P. fluorescens (Zhang and Rainey, 2007 , 2008 ; Zhang et al, 2015 ) and glucose uptake in Azotobacter vinelandii (Quiroz-Rocha et al, 2017 ). The CbrAB system also participates in carbon catabolite repression control (Görke and Stülke, 2008 ).…”

Expression of the sRNAs CrcZ and CrcY modulate the strength of carbon catabolite repression under diazotrophic or non-diazotrophic growing conditions in Azotobacter vinelandii

“…vinelandii CCR system operates similarly to that present in Pseudomonas species. In the diauxic acetate-glucose growth, acetate (the preferred carbon source) was consumed first [5]. Our results indicated that under this condition expression of the glucose GluP transporter was suppressed, but this repression was released once the acetate was exhausted, allowing the uptake of glucose and the growth at the expense of this secondary carbon source.…”

“…A . vinelandii prefers the use of organic acids rather than carbohydrates, hence in a mix of acetate-glucose, acetate prevents the utilization of glucose [3–5]. This preferential use is regulated by the Carbon Catabolite Repression (CCR) that inhibits expression of genes required for degradation/metabolism of the less preferred substrates [6, 7].…”

Influence of the Hfq and Crc global regulators on the control of iron homeostasis in Pseudomonas putida

“…Inactivation of the hfq gene in P. aeruginosa also results in pleiotropic effects that influence cell motility and growth under anoxic conditions, as well as causing redox imbalances, altered quorum-sensing responses and significantly attenuated virulence (Sonnleitner et al, 2003;Sonnleitner et al, 2006;Pusic et al, 2016). In pseudomonads, Hfq assists the annealing of regulatory sRNAs to their target mRNAs (Ferrara et al, 2015), but part of its regulatory function is performed in cooperation with the Crc (catabolite repression control) protein, which has been found only in this bacterial group and certain related genera (reviewed in Rojo, 2010; see also Quiroz-Rocha et al, 2017). Crc is a global regulator that modulates the expression of many genes, helping to control carbon metabolism.…”