AUTHOR=Chen Si , Zhou Qing , Tan Xin , Li Ye , Ren Ge , Wang Xiaoyuan 

TITLE=The Global Response of Cronobacter sakazakii Cells to Amino Acid Deficiency

JOURNAL=Frontiers in Microbiology

VOLUME=9

YEAR=2018

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2018.01875

DOI=10.3389/fmicb.2018.01875

ISSN=1664-302X

ABSTRACT=<p><italic>Cronobacter</italic> species can cause necrotizing enterocolitis and meningitis in neonates and infants, their infection is closely relevant to their responses to extreme growth conditions. In this study, the response of <italic>Cronobacter</italic> species to amino acid deficiency has been investigated. Four <italic>Cronobacter</italic> species formed smooth colonies when grown on the solid LB medium, but formed mucoid colonies when grown on the amino acid deficient M9 medium. When the mucoid colonies were stained with tannin mordant, exopolysaccharide around the cells could be discerned. The exopolysaccharide was isolated, analyzed, and identified as colanic acid. When genes <italic>wcaD</italic> and <italic>wcaE</italic> relevant to colanic acid biosynthesis were deleted in <italic>Cronobacter sakazakii</italic> BAA-894, no exopolysaccharide could be produced, confirming the exopolysaccharide formed in <italic>C. sakazakii</italic> grown in M9 is colanic acid. On the other hand, when genes <italic>rcsA</italic>, <italic>rcsB</italic>, <italic>rcsC</italic>, <italic>rcsD</italic>, or <italic>rcsF</italic> relevant to Rcs phosphorelay system was deleted in <italic>C. sakazakii</italic> BAA-894, colanic acid could not be produced, suggesting that the production of colanic acid in <italic>C. sakazakii</italic> is regulated by Rcs phosphorelay system. Furthermore, <italic>C. sakazakii</italic> BAA-894 grown in M9 supplemented with amino acids could not produce exopolysaccharide. Transcriptomes of <italic>C. sakazakii</italic> BAA-894 grown in M9 or LB were analyzed. A total of 3956 genes were differentially expressed in M9, of which 2339 were up-regulated and 1617 were down-regulated. When <italic>C. sakazakii</italic> BAA-894 was grown in M9, the genes relevant to the biosynthesis of exopolysaccharide were significantly up-regulated; on the other hand, the genes relevant to the flagellum formation and chemotaxis were significantly down-regulated; in addition, most genes relevant to various amino acid biosynthesis were also significantly regulated. The results demonstrate that amino acid deficiency has a global impact on <italic>C. sakazakii</italic> cells.</p>