Anr, the anaerobic global regulator, modulates the redox state and oxidative stress resistance in Pseudomonas extremaustralis

Abstract

The role of Anr in oxidative stress resistance was investigated in Pseudomonas extremaustralis, a polyhydroxybutyrate-producing Antarctic bacterium. The absence of Anr caused increased sensitivity to hydrogen peroxide under low oxygen tension. This phenomenon was associated with a decrease in the redox ratio, higher oxygen consumption and higher reactive oxygen species production. Physiological responses of the mutant to the oxidized state included an increase in NADP(H) content, catalase activity and exopolysaccharide production. The wild-type strain showed a sharp decrease in the reduced thiol pool when exposed to hydrogen peroxide, not observed in the mutant strain. In silico analysis of the genome sequence of P. extremaustralis revealed putative Anr binding sites upstream from genes related to oxidative stress. Genes encoding several chaperones and cold shock proteins, a glutathione synthase, a sulfate transporter and a thiol peroxidase were identified as potential targets for Anr regulation. Our results suggest a novel role for Anr in oxidative stress resistance and in redox balance maintenance under conditions of restricted oxygen supply.

Dual promoters of the major catalase (KatA) govern distinct survival strategies of Pseudomonas aeruginosa

“…Moreover, the katAp2 transcript was slightly reduced upon H 2 O 2 treatment ( Fig. 1A ; see below), which is in a good agreement with the fact that the Fe-S center of Anr is vulnerable to ROS and RNS with its transactivation activity compromised in the presence of O 2 − , H 2 O 2 , and NO 13 14 15 .…”

“…Another important contribution of this work is to provide a new picture to associate the protective functions of KatA with its regulation governed by OxyR and Anr. It should be noted that OxyR and Anr work apparently under the opposite conditions: for example, OxyR is activated by H 2 O 2 or NO 26 , while Anr is inactivated by H 2 O 2 or NO, because its Fe-S cluster is vulnerable to H 2 O 2 and NO 13 14 15 . Nevertheless, the dual promoters ensure the katA transcription in both balanced (i.e.…”

The global regulator Crc orchestrates the metabolic robustness underlying oxidative stress resistance in Pseudomonas aeruginosa

“…carbon and nitrogen sources) and O 2 (Palmer et al, 2007;La Rosa et al, 2018) and bacterial cells often have to face other challenges simultaneously, such as the presence of multispecies microbiota and several types of stress factors, for example, immune responses, antibiotics and oxidative and osmotic stress (Moradali et al, 2017). Sophisticated regulatory networks in Pseudomonads control the physiological responses to these stressful conditions, including both local and global regulators that adjust transcriptional levels according to environmental cues (Tribelli et al, 2013;Balasubramanian et al, 2015;Arce-Rodríguez et al, 2016;Udaondo et al, 2018). Carbon catabolite repression, governed by the Crc protein, is a major player among these regulatory systems in Pseudomonas species (Wolff et al, 1991;Collier et al, 1996;Velázquez et al, 2004;Rojo, 2010;Grenga et al, 2017;Liu et al, 2017;Wirebrand et al, 2018).…”

The Global Anaerobic Regulator Anr, Is Involved in Cell Attachment and Aggregation Influencing the First Stages of Biofilm Development in Pseudomonas extremaustralis

“…A complemented strain was constructed as described before, by inserting the entire wild type anr sequence in the mutant by using a mini-Tn5 delivery system [21]. All cultures were performed using 0.5 NE2 medium supplemented with 0.2% glucose, 0.3%, casaminoacids, 0.08% KNO 3 , 1 mM MgSO 4 and 0.1% micronutrients [28].…”

“…In Pseudomonas , the redox global regulator Anr controls anaerobic metabolism by activation and repression of targets genes. Denitrification, arginine and pyruvate fermentation, redox state maintenance, fimbria and cytochrome biosynthesis, secretion type III system, oxidative stress resistance and quorum sensing cascades are some of the functions that are known to be modulated by Anr [15], [16], [17], [18], [19], [20], [21], [22]. The role of global regulator Anr in biofilm development in non-pathogenic Pseudomonas species has not been studied yet.…”