Stigmatella aurantiaca

Stigmatella aurantiaca is a member of myxobacteria, a group of gram-negative bacteria with a complex developmental life cycle. The bacterial nature of this organism was recognized by Thaxter in 1892, who grouped it among the Chrondromyces. It had been described several times before, but had been misclassified as a member of the fungi imperfecti. More recent investigations have shown that, contrary to Thaxter's classification, this organism is not closely related to Chrondromyces, and Stigmatella is currently recognized as a separate genus. Of the three major subgroups of the myxobacteria, Myxococcus, Nannocystis, and Chrondromyces, Stigmatella is most closely aligned with Myxococcus. S. aurantiaca, like other myxobacterial species, has a complex life cycle including social gliding (swarming), fruiting body formation, and predatory feeding behaviors. The bacteria do not swim, but glide on surfaces leaving slime trails, forming a mobile biofilm. It commonly grows on the surface of rotting soft woods or fungi, where it may form bright orange patches. During the vegetative portion of their life cycles, swarming enables coordinated masses of myxobacteria to pool their secretions of extracellular digestive enzymes which are used to kill and consume prey microorganisms, a bacterial 'wolfpack' effect. The best studied of the myxobacteria, Myxococcus xanthus, has been shown to actively surround prey organisms, trapping them in pockets where they can be consumed. Roaming flares of M. xanthus can detect clumps of prey bacteria at a distance, making turns towards the clumps and moving directly towards them. Like other myxobacterial species, S. aurantiaca survives periods of starvation by undergoing a developmental process whereby the individuals of a swarm aggregate to form fruiting bodies (not to be confused with those in fungi). Within the fruiting bodies, a certain fraction of the cells differentiate into myxospores, which are dormant cells resistant to drying and temperatures up to 90 °C. Differentiation into fruiting bodies appears to be mediated by contact-mediated signaling. Under laboratory growth conditions, the ability to undergo differentiation to form fruiting bodies is rapidly lost unless the cultures are regularly forced to fruit by transferring to starvation media. Shaker cultures of S. aurantiaca permanently lose the ability to fruit. The complex life cycle of myxobacteria is reminiscent of the life cycle of eukaryotic cellular slime molds. Taxonomic identifier: 378806