The Genus Lysobacter
The species classified in the genus Lysobacter are Gram-negative rods that move by gliding. The cells are slender and cylindrical, with rounded ends (Figs. 1 and 2 ). They typically measure 0.4–0.6 × 2–5 µm, but in the population there are also always lon
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The Genus Lysobacter HANS REICHENBACH
The species classified in the genus Lysobacter are Gram-negative rods that move by gliding. The cells are slender and cylindrical, with rounded ends (Figs. 1 and 2). They typically measure 0.4– 0.6 × 2–5 µm, but in the population there are also always long to very long (up to 70 µm) cells and filaments. The cell shape and the occurrence of long cells are both very characteristic for the genus. Lysobacter cells resemble the vegetative cells of certain myxobacteria, specifically of the genera Polyangium and Sorangium, with which the lysobacters were confused for many years. They also share with the myxobacteria a high GC content of their DNA of 65 to 70 mol%. Due to the gliding movements of the cells, the colonies of Lysobacter are spreading or swarming on solid media and may become very large and extremely thin Figs. 3 and 4). Sometimes the organisms produce copious amounts of slime, and the colonies then become thick and deliquescent, but colonies with a wrinkled and dry surface also occur. Lysobacter colonies may be white or cream-colored but often they are greenishyellow, purplish-red, or brown, although their color is often rather pale. Some strains produce an unpleasant odor reminiscent of certain pseudomonads or of pyridine. In agitated liquid cultures, the lysobacters grow as homogeneous cell suspensions, but, as with all gliding bacteria, the suspended cells are unable to translocate. The Lysobacter species live in soil, decaying organic matter, and fresh water, sometimes in large populations. Many strains are of considerable ecological and biotechnological interest as producers of exoenzymes and of antibiotics. The genus Lysobacter was defined by Christensen and Cook (1978) who also described the presently recognized species and created a new family, Lysobacteraceae, and a new order, Lysobacterales. The organisms thus classified had already been known, however, for a long time under various names, such as Cytophaga, Sorangium, and Myxobacter (the latter an obsolete myxobacterial genus), which were usually preThis chapter was taken unchanged from the second edition.
sented with some doubts of the investigators concerning the classification of their strains. The first lysobacter in the scientific literature may have been Flexibacter albuminosus (Soriano, 1945, 1947), which had the cell size and shape of a lysobacter and formed thick dirty-white colonies and a diffusible dark pigment. But the description is not accurate enough and the strains are no longer available so that the question cannot be decided. The first unequivocal Lysobacter strain was a chitinolytic strain first tentatively identified as Cytophaga johnsonae Veldkamp, (1955). It is deposited at the National Collection of Industrial Bacteria (NCIB no. 8501) and was originally listed as a Polyangium species. The strain has a GC content of 71 mol% (Tm) and was noted as an unusual case of a cytophaga with a high GC content (Mitchell et al., 1969). Other early strains that later turned
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