A ς ⁵⁴ Activator Protein Necessary for Spore Differentiation within the Fruiting Body of Myxococcus xanthus

Abstract

Insertion of an internal DNA fragment into the act1 gene, which encodes one of several 54 -activator proteins in Myxococcus xanthus, produced a mutant defective in fruiting body development. While fruiting-body aggregation appears normal in the mutant, it fails to sporulate (<10 ؊6 the wild-type number of viable spores). The A and C intercellular signals, which are required for sporulation, are produced by the mutant. But, while it produces A-factor at levels as high as that of the wild type, the mutant produces much less C-signal than normal, as measured either by C-factor bioassay or by the total amount of C-factor protein detected with specific antibody. Expression of three C-factor-dependent reporters is altered in the mutant: the level of expression of ⍀4414 is about 15% of normal, and ⍀4459 and ⍀4403 have alterations in their time course. Finally, the methylation of FrzCD protein is below normal in the mutant. It is proposed that Act1 protein responds to C-signal reception by increasing the expression of the csgA gene. This C-signal-dependent increase constitutes a positive feedback in the wild type. The act1 mutant, unable to raise the level of csgA expression, carries out only those developmental steps for which a low level of C-signaling is adequate.

Cell Death in Pseudomonas aeruginosa Biofilm Development

“…We hypothesized that genes that control fruiting body development and cell death in M. xanthus may similarly influence P. aeruginosa development. In M. xanthus, development of fruiting bodies is controlled in part by RpoN (21,22) and by cell-cell signaling (54). In P. aeruginosa, microcolony development is also influenced by RpoN (61) and cell-cell signaling (13).…”

“…It is possible that expression of receptors for the phage is developmentally regulated, as is the case for type IV pili in M. xanthus (69). Indeed, RpoN controls morphogenesis and development in M. xanthus and also regulates T4P and flagella in P. aeruginosa (21,22,62). T4P have also been reported to be downregulated during P. aeruginosa biofilm development (66).…”

Role of fruA and csgA Genes in Gene Expression during Development of Myxococcus xanthus

“…This results in highly phosphorylated FruA, allowing the expression of fruA-dependent/csgA-dependent genes. The csgA expression is fully activated by its own product (21,(35)(36)(37). ess.…”

Identification of an activator protein required for the induction of fruA , a gene essential for fruiting body development in Myxococcus xanthus

“…On the other hand, the activity of FruA also seems to be regulated by CsgA (C-signal) (6). C-signal also has been proposed to activate the act operon, whose products regulate the level of CsgA protein (34)(35)(36)(37). As the developmental program proceeds and the concentration of C-signal increases, more FruA becomes phosphorylated and induces the expression of C-signal-dependent genes, which leads to FrzCD methylation and devTRS expression (4,6,38).…”