Department of Microbiology, University of Manitoba, Winnipeg, MB R3T 2N2, Canada.
Department of Biosystems Engineering, University of Manitoba, Winnipeg, MB R3T 2N2, Canada.
Can J Microbiol. 2021 Jun;67(6):476-490. doi: 10.1139/cjm-2020-0497. Epub 2021 May 31.
PA23 is a biocontrol agent capable of protecting canola against the fungal pathogen . In addition to producing antifungal compounds, this bacterium synthesizes and accumulates polyhydroxyalkanoate (PHA) polymers as carbon and energy storage compounds. Because the role of PHA in PA23 physiology is currently unknown, we investigated the impact of this polymer on stress resistance, adherence to surfaces, and interaction with the protozoan predator . Three PHA biosynthesis mutants were created, PA23, PA23, and PA23, which accumulated reduced PHA. Our phenotypic assays revealed that PA23 produced less phenazine (PHZ) compared with the wild type (WT) and the and mutants. All three mutants exhibited enhanced sensitivity to UV irradiation, starvation, heat stress, cold stress, and hydrogen peroxide. Moreover, motility, exopolysaccharide production, biofilm formation, and root attachment were increased in strains with reduced PHA levels. Interaction studies with the amoeba revealed that the WT and the and mutants were consumed less than the mutant, likely due to decreased PHZ production by the latter. Collectively these findings indicate that PHA accumulation enhances PA23 resistance to a number of stresses in vitro, which could improve the environmental fitness of this bacterium in hostile environments.
PA23 是一种能够保护油菜免受真菌病原体侵害的生物防治剂。除了产生抗真菌化合物外，这种细菌还合成并积累聚羟基烷酸酯（PHA）聚合物作为碳和能量储存化合物。由于 PHA 在 PA23 生理学中的作用目前尚不清楚，我们研究了这种聚合物对抵抗压力、附着在表面上以及与原生动物捕食者相互作用的影响。创建了三个 PHA 生物合成突变体，PA23、PA23 和 PA23，它们积累了减少的 PHA。我们的表型分析表明，与野生型（WT）和 和 突变体相比，PA23 产生的吩嗪（PHZ）较少。所有三个突变体对紫外线照射、饥饿、热应激、冷应激和过氧化氢的敏感性增强。此外，降低 PHA 水平的菌株的运动性、胞外多糖产生、生物膜形成和根附着增加。与变形虫 的相互作用研究表明，WT 和 和 突变体比 突变体消耗得更少，这可能是由于后者 PHZ 产生减少所致。总之，这些发现表明 PHA 积累增强了 PA23 对体外多种压力的抵抗力，这可能提高了这种细菌在恶劣环境中的环境适应性。
