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The bcsA gene influences multiple aspects of development in Myxococcus xanthus.

M. xanthus strains containing a mutation in the bcsA gene are able to bypass the B and C signaling requirements for development. The bcsA mutant was examined with regards to several aspects of development to better ascertain the function of the bcsA gene. The bcsA mutant developed on nutrient levels sufficient to support vegetative growth in wild-type cells, supporting previous evidence that the bcsA gene inhibits development. The earliest effect of the bcsA mutation on the development program was when cells were beginning to aggregate together to form fruiting bodies. Spores produced by bcsA mutants were hypersusceptible to sodium dodecyl sulfate, suggesting that the bcsA gene is important for optimal spore production. Transcription of the bcsA gene was induced significantly during development at a time when cells were beginning to aggregate together. Collectively, these results indicate that the bcsA gene inhibits development and is also transcriptionally upregulated during development.

Anti-Bacterial Agents↗

Multicellular development and gliding motility in Myxococcus xanthus.

A great deal of progress has been made in the studies of fruiting body development and social gliding in Myxocococcus xanthus in the past few years. This includes identification of the bone fide C-signal and a receptor for type IV pili, and development of a model for the mechanism of adventurous gliding motility. It is anticipated that the next few years will see even more progress as the complete genome sequence is available and genomic and proteomic tools are applied to the study of M. xanthus social behaviors.

Movement↗

Protein W, a spore-specific protein in Myxococcus xanthus, formation of a large electron-dense particle in a spore.

The gene for the major spore-specific protein, termed protein W, was cloned, and it was found that protein W is composed of 426 amino acid residues including 31% charged (133 residues) and 39% hydrophobic (166 residues) amino acids. In the protein, a motif consisting of five amino acid residues [(V/L/I)-R-E-R-(V/L/I)] is repeated 28 times, and another motif [M-M-(P/G)-Q-G] five times. Protein W is synthesized during a very late stage of development, forming a single, large electron-dense particle (200-400 nm in diameter) inside a spore. X-ray microanalysis of the particle revealed that it contains a high amount of phosphate in addition to calcium and magnesium. It is proposed that protein W consisting of highly charged repetitive sequences is a polyphosphate storage protein to store energy in spores. The disruption of the gene for protein W resulted in delayed fruiting body formation and a lower spore yield.

Amino Acid Sequence↗

The act operon controls the level and time of C-signal production for Myxococcus xanthus development.

The C-signal is a morphogen that controls the assembly of fruiting bodies and the differentiation of myxospores. Production of this signal, which is encoded by the csgA gene, is regulated by the act operon of four genes that are co-transcribed from the same start site. The act A and act B genes regulate the maximum level of the C-signal, which never rises above one-quarter of the maximum wild-type level of CsgA protein in null mutants of either gene. The act A and act B mutants have the same developmental phenotype: both aggregate, neither sporulates, both prolong rippling. By sequence homology, act A encodes a response regulator, and act B encodes a sigma-54 activator protein of the NTRC class. The similar phenotypes of act A and act B deletion mutants suggest that the two gene products are part of the same signal transduction pathway. That pathway responds to C-signal and also regulates the production of CsgA protein, thus creating a positive feedback loop. The act C and act D genes regulate the time pattern of CsgA production, while achieving the same maximum level. An act C null mutant raises CsgA production 15 h earlier than the wild type, whereas an act D null mutant does so 6 h later than wild type. The loop explains how the C-signal rises continuously from early development to a peak at the time of sporulation, and the act genes govern the time course of that rise.

Bacterial Proteins↗