Division of Microbiology and Biotechnology, Yenepoya Research Centre, Yenepoya (Deemed to be University), University Road, Deralakatte, Mangalore 575018, India.
Division of Microbiology and Biotechnology, Yenepoya Research Centre, Yenepoya (Deemed to be University), University Road, Deralakatte, Mangalore 575018, India; Yenepoya Institute of Arts, Science, Commerce and Management, Balmatta, Mangalore 575002, India.
Microbiol Res. 2022 Oct;263:127142. doi: 10.1016/j.micres.2022.127142. Epub 2022 Jul 26.
Urea is one of the major components of the human urine and its breakdown by the uropathogens occurs mainly through the activity of the enzyme urease. However, a few reports suggest the presence of an alternate enzyme system for urea breakdown namely urea carboxylase (UC) and allophanate hydrolase (AH). We have previously reported the UC and AH system in the genome of a urease-negative uropathogen Kalamiella piersonii YU22 of the novel genus Kalamiella (reclassified recently as Pantoea).To validate the UC and AH activity in the presence of urea, we investigated the growth and urea utilization patterns of this bacterium. Growth kinetics, variations in media pH, NH-N generation and UC and AH gene expressions were probed using urea-containing media. YU22 was able to grow in M9 media containing urea and increase the pH of the media due to the urea breakdown. Further, significantly higher concentrations of extracellular NH-N (p < 0.001) was also detected in the cultures along with over-expression of UC and AH genes. The bacterium formed biofilm, and displayed swimming and swarming motilities in presence of urea. Additional glucose supply to urea boosted the colonization but ameliorated the media alkalization and ammonification through suppression of gene expressions encoding UC and AH. These results show that the urease-negative strain YU22 can utilize the UC and AH system for urea metabolism. We propose to further investigate the UC and AH system in other urease-negative uropathogens and its implications for pathogenicity and urinary tract colonization.
尿素是人体尿液的主要成分之一，其在尿路病原体中的分解主要通过酶脲酶的活性来实现。然而，有一些报道表明存在一种替代的尿素分解酶系统，即尿素羧化酶 (UC) 和异丁烯酸脲水解酶 (AH)。我们之前已经在脲酶阴性尿路病原体 Kalamiella piersonii YU22 的基因组中报道了 UC 和 AH 系统，该病原体属于新属 Kalamiella（最近重新分类为 Pantoea）。
为了验证 UC 和 AH 在尿素存在下的活性，我们研究了该细菌的生长和尿素利用模式。使用含有尿素的培养基研究了该细菌的生长动力学、培养基 pH 值变化、NH-N 的产生以及 UC 和 AH 基因的表达情况。YU22 能够在含有尿素的 M9 培养基中生长，并由于尿素的分解而增加培养基的 pH 值。此外，还检测到培养基中细胞外 NH-N 的浓度显著升高（p<0.001），同时 UC 和 AH 基因的表达也上调。该细菌形成生物膜，并在有尿素存在的情况下表现出泳动和群集运动能力。向尿素中额外添加葡萄糖可促进定植，但通过抑制编码 UC 和 AH 的基因的表达来减轻培养基的碱化和氨化。
这些结果表明，脲酶阴性菌株 YU22 可以利用 UC 和 AH 系统进行尿素代谢。我们建议进一步研究其他脲酶阴性尿路病原体中的 UC 和 AH 系统及其对致病性和尿路感染定植的影响。
