Deletion of the cell-division inhibitor MinC results in lysis of Neisseria gonorrhoeae

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Abstract
The minCDE genes involved in division site selection in Neisseria gonorrhoeae were identified using raw data from the N. gonorrhoeae genome project and are part of a cluster of 27 genes. When gonococcal min genes were heterologously expressed as a cluster in Escherichia coli, minicells and filaments were produced, indicating that gonococcal min genes disrupted cell division in other genera. The insertional inactivation of the minC gene of N. gonorrhoeae CH811 resulted in a strain (CSRC1) with decreased viability and grossly abnormal cell division as observed by phase-contrast and electron microscopy analysis. Western blot analysis of N. gonorrhoeae CSRC1 confirmed that MinCNg was not produced. Complementation of CSRC1 by integrating a minC–6×His tag fusion at the proAB locus by homologous recombination restored viability and 1·9 times wild-type levels of MinCNg expression. This slight increase of expression caused a small percentage of the complemented cells to divide aberrantly. This suggested that the 6×His tag has partially affected the stability of MinC, or that the chromosomal position of minC is critical to its regulation. Comparison of MinC proteins from different bacteria showed a homologous region corresponding to residues 135–230 with five conserved amino acids. Overexpression of MinCNg in wild-type E. coli cells induced filamentation and an E. coli minC mutant was successfully complemented with minC Ng. Therefore, the evidence indicates that MinC from N. gonorrhoeae acts as a cell-division inhibitor and that its role is essential in maintaining proper division in cocci.