Genes for four nearly identical PKc-like proteins were downregulated in WT-T, asgB and xre228. Gene expression was repressed to a similar extent for each gene, which suggests that their regulation may be coordinated and that they may encode redundant functions. The similarity between these proteins and the proximity of each to a S_TPk suggests that these clusters are the result of gene duplication. Such regions of the chromosome may be targets for gene conversion, a known mechanism for regulating phase variation. In contrast with the PKc-like genes, expression of S_TPk genes was increased in WT-T and asgB. This group of S_TPk may function in pathways involving motility or development, which are impacted in WT-T and asgB. The ability of M. xanthus to generate two distinct cell types depending on the availability of iron makes sense given the social nature and habitats of this organism. M. xanthus has been compared to higher order social organisms, including bees and ants, that live in large groups and cooperate through a division of labor to accomplish complex tasks. As M. xanthus colonies normally contain a mixture of yellow and tan cell types, phase variation takes on a mutualistic quality. During growth, yellow variants accumulate at the colony edge and surround the slower swarming tan variants. Elevated levels of DKX and Mxv, which are needed for sporulation and predation, respectively, likely benefit tan variants. In return, elevated levels of FeNsiderophore produced by tan variants may benefit yellow variants. When nutrient depletion induces the development cycle, tan variants enriched near the colony center and bathed in chemicals, such as DKX, from yellow variants are well positioned to differentiate into spores. Maintenance of both yellow and tan cell types with minimal ��cheating�� may be safeguarded by the fact that the potentially CK-636 iron-rich tan cells need DKX for efficient spore production. As only yellow cells produce the DKX ML130 pigment, their survival is guaranteed. The chip was washed and then scanned on a Roche MS200 scanner.