Investigating the role of the bacterial mechanosensitive channel YnaI in Salmonella pathogenesis

Mechanosensitive channels are required for bacteria cells to survive hypoosmotic shock (transition from high to low osmolarity environment). YnaI is one of the mechanosensitive channels found amongst many bacterial species including Salmonella Typhimurium. Previous studies have suggested that S. Typhimurium YnaI may be implicated in host colonization during infection of farmed animals. Disruption of ynaI impaired intestinal colonization in pigs, cattle and chicken. To investigate S. Typhimurium YnaI structure and function, the S.Typhimurium ynaI was cloned into a plasmid, followed by physiological characterization of the S. Typhimurium YnaI constructs expressed in an E. coli channel-less mutant strain. To further understand the role of YnaI in S. Typhimurium pathogenesis, S. Typhimurium ynaI was deleted and the ability of mutant to survive and replicate in host cells was investigated. The S. Typhimurium YnaI channel has unique characteristics when expressed in E. coli: S. Typhimurium YnaI channel conferred almost complete protection against 0.3 M NaCl hypoosmotic shock when overexpressed, but interestingly, high level expression of S. Typhimurium YnaI inhibited growth in two different complex media and in minimal media. Deletion of ynaI from S. Typhimurium led to increased internalization in macrophages and epithelial cells. Data derived from this study reveals novel characteristics of S. Typhimurium YnaI which may provide insights into other functions of the S. Typhimurium YnaI channel.