Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan, USA.
J Bacteriol. 2013 Mar;195(6):1305-19. doi: 10.1128/JB.02136-12. Epub 2013 Jan 11.
Proteus mirabilis, a leading cause of catheter-associated urinary tract infection (CaUTI), differentiates into swarm cells that migrate across catheter surfaces and medium solidified with 1.5% agar. While many genes and nutrient requirements involved in the swarming process have been identified, few studies have addressed the signals that promote initiation of swarming following initial contact with a surface. In this study, we show that P. mirabilis CaUTI isolates initiate swarming in response to specific nutrients and environmental cues. Thirty-three compounds, including amino acids, polyamines, fatty acids, and tricarboxylic acid (TCA) cycle intermediates, were tested for the ability to promote swarming when added to normally nonpermissive media. L-Arginine, L-glutamine, DL-histidine, malate, and DL-ornithine promoted swarming on several types of media without enhancing swimming motility or growth rate. Testing of isogenic mutants revealed that swarming in response to the cues required putrescine biosynthesis and pathways involved in amino acid metabolism. Furthermore, excess glutamine was found to be a strict requirement for swarming on normal swarm agar in addition to being a swarming cue under normally nonpermissive conditions. We thus conclude that initiation of swarming occurs in response to specific cues and that manipulating concentrations of key nutrient cues can signal whether or not a particular environment is permissive for swarming.
奇异变形杆菌是导致导尿管相关尿路感染 (CAUTI) 的主要原因之一，它可分化为群集细胞，这些细胞可迁移到导管表面和用 1.5%琼脂固化的培养基中。虽然已经确定了许多与群集过程相关的基因和营养需求，但很少有研究涉及促进与表面初始接触后群集启动的信号。在这项研究中，我们表明奇异变形杆菌 CAUTI 分离株会响应特定的营养物质和环境线索启动群集。测试了 33 种化合物，包括氨基酸、多胺、脂肪酸和三羧酸 (TCA) 循环中间产物，以确定它们在添加到通常不允许的培养基中时是否能够促进群集。L-精氨酸、L-谷氨酰胺、DL-组氨酸、苹果酸和 DL-鸟氨酸在几种类型的培养基中促进群集，而不会增强泳动运动或生长速率。同基因突变体的测试表明，对这些线索的群集反应需要腐胺生物合成和涉及氨基酸代谢的途径。此外，除了在通常不允许的条件下作为群集线索外，还发现过量的谷氨酰胺是在正常群集琼脂上群集的严格要求。因此，我们得出结论，群集的启动是对特定线索的响应，并且操纵关键营养线索的浓度可以表明特定环境是否允许群集。
