Essential role of K⁺ uptake permease (Kup) for resistance to sucrose‐induced stress in Gluconacetobacter diazotrophicus PAl 5

Abstract

Microorganisms are constantly challenged by stressful conditions, such as sugar-rich environments. Such environments can cause an imbalance of biochemical activities and compromise cell multiplication. Gluconacetobacter diazotrophicus PAl 5 is among the most sugar-tolerant bacteria, capable of growing in the presence of up to 876 mM sucrose. However, the molecular mechanisms involved in its response to high sucrose remain unknown. The present work aimed to identify sucrose-induced stress resistance genes in G. diazotrophicus PAl 5. Screening of a Tn5 transposon insertion library identified a mutant that was severely compromised in its resistance to high sucrose concentrations. Molecular characterization revealed that the mutation affected the kupA gene, which encodes a K uptake transporter (KupA). Functional complementation of the mutant with the wild type kupA gene recovered the sucrose-induced stress resistance phenotype. High sucrose resistance assay, under different potassium concentrations, revealed that KupA acts as a high-affinity K transporter, which is essential for resistance to sucrose-induced stress, when extracellular potassium levels are low. This study is the first to show the essential role of the KupA protein for resistance to sucrose-induced stress in bacteria by acting as a high-affinity potassium transporter in G. diazotrophicus PAl 5.

Regulation of potassium homeostasis inCaulobacter crescentus

“…4C and D , Tables S1 and S2 ). Kup has been described in different bacteria as the major K + transporter, essential in hyperosmotic conditions using sucrose as osmotic stressor (38, 39). Moreover, in a previous study, we found that the TCS ChvGI in C. crescentus positively controls the expression of kup in hyperosmotic conditions (37).…”

“…4B, Tables S1 and S2). Kup has been described in different bacteria as the major K + transporter, essential in hyperosmotic conditions using sucrose as osmotic stressor (de Oliveira et al, 2017, Trchounian & Kobayashi, 1999.…”

Non-nodular Endophytic Bacterial Symbiosis and the Nitrogen Fixation of Gluconacetobacter diazotrophicus

“…diazotrophicus is one of the relatively few bacteria capable of being cultured at very high sucrose concentrations (876 mM sucrose [28]; 30% [29]) and can tolerate a water activity level of 0.892 aw [26]. This is perhaps not surprising given its host plant, sugarcane and other high sucrose content host plants from which it has been isolated ( Table 1), but for G. diazotrophicus to tolerate sucrose-induced stress, it has to have the mechanisms with which to cope.…”