Page:Bergey's manual of determinative bacteriology.djvu/298

 ORDER III. HYPHOMICROBIALES DOUGLAS,

Hy.pho.mi.cro.bi.a'les. M.L. fem.pl. n. Hyphomicrobiaceae type family of the order; -ales ending to denote an order; M.L. fem.pl.n. Hyphomicrobiales the Hyphomicrobiaceae order.

Multiplication is by budding or by budding and longitudinal fission. Buds may be sessile or may be borne at the tip of a slender filament which arises from the pole of a mature cell or from a filament connecting two cells. Cells may occur singly or in pairs but are found more commonly in aggregates. In some types the aggregates consist of groups of cells attached to a surface by stalks which appear to radiate from a common holdfast; in others the aggregates consist of free-floating cell groups in which the cells are attached to one another by the filament engendered in the budding process. Branching of the filament may result in groups which contain several hundred cells. Cells are ovoid, ellipsoidal, spherical or pyriform. If motile, the cells possess a single polar flagellum. Specialized resting stages have not been found. Gram-negative so far as known. Metabolism may be heterotrophic or photosynthetic. Found in the mud and water of fresh-water ponds and streams; also parasitic on fresh-water crustacea.


 * I. Buds borne upon filaments.


 * II. Buds sessile.

Hy.pho.mi.cro.bi.a'ce.ae. M.L. neut.n. Hyphomicrobium type genus of the family; -aceae ending to denote a family; M.L. fem.pl.n. Hyphomicrobiaceae the Hyphomicrobium family.

These organisms occur mainly as free-floating groups in which the cells are attached to one another by a slender, sometimes branched, filament. Daughter-cell formation is initiated by the outgrowth of a filament from the pole of a mature cell or from some point on a filament connecting two mature cells. The daughter cell is formed by enlargement of the tip of the filament. Gram-negative.

I. Chemoheterotrophic. Motile.