Numerical taxonomic, DNA-DNA hybridization, and phospholipid fatty acid composition analyses were performed on an extensive range of methanotrophic strains, including reference strains and environmental

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Summary The exploration of new source materials and the use of alternative isolation and identification methods have led to rapid expansion in the knowledge of diversity; in Lysobacter, 11 new species having been described since 2005, and in Stenotrophomonas with six new species since 2000. The new species of Lysobacter, isolated by dilution and direct plating on standard media, differ in several key phenotypic properties from those obtained by enrichment on complex polysaccharides in the original description of the genus. Revision of the definition of the genus will be required. Both culture‐dependent and culture‐independent methods to assess community structure, in a variety of host and nonhost environments, have established that some species of Lysobacter are a dominant component of the microflora, where previously their presence had not been suspected. Culture‐independent studies have generally not added new information on the occurrence and distribution of Stenotrophomonas maltophilia and other members of the genus, which are readily isolated on standard media from source materials. Lysobacter enzymogenes and Sten. maltophilia produce similar antibiotics and share some enzyme activities which, subject to safety considerations, may make them attractive candidates for use in biological control of plant diseases and of nematodes.

Bacteria in sediments from the surface aerobic layer (0-1 cm) and a deeper anaerobic layer (20-21 cm) of a seagrass bed were examined in section by transmission electron microscopy. Bacteria with a Gram-negative ultrastructure made up 90% of bacteria in the surface layer, and Gram-positive bacteria comprised 10%. In the anaerobic zone, Gram-negative bacteria comprised 70% and Gram-positive bacteria 30% of the bacterial population. These differences were highly significant and support predictions of these proportions made from muramic acid measurements and direct counting with fluorescence microscopy. Most cells were enveloped in extracellular slime layers or envelopes, some with considerable structural complexity. The trophic value to animals of these envelopes is discussed. A unique organism with spines was observed.

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Organisms of two strains of Pseudomonas stizolobii possessed one polar flagellum of unusual thickness. Negative-contrast staining and ultrathin sectioning indicated that the flagella are sheathed and are comparable in structure to the sheathed flagella described in Vibrio and Bdellovibrio. In some instances, flagella displayed sheath and core structure after negative constrast staining. Distal 'tubules ' and ' knobs ' apparently consisting entirely of sheath material were also seen. The thickness of the sheath, which in section consisted of an outer dense component and an inner lighter component, was similar to that of the outer double track membrane of the cell wall. I N T R O D U C T I O NDuring the examination of a collection of species of Pseudomonas for the presence of fimbria-like appendages (Fuerst & Hayward, 1969), unusual polar flagella were seen on Pseudomonas stizolobii (Wolf) Stapp, 1935. This species is a plant pathogen causing a disease of the leaves and stems of mainly leguminous plants (Burkholder, 1957;Rothwell & Hayward, 1964). Whereas flagella of most bacteria are 120 to 150 A in diameter and, under the electron microscope at high resolution, preparations of negatively stained material exhibit a helical aggregate of globular subunits, (Joys, 1968 ;Doetsch & Hageage, 1968), the flagella of P. stizolobii were of greater thickness and lacked the substructure characteristic of unsheathed bacterial flagella. Our aim was to determine by electron microscopic techniques the nature of the flagellum of P. stizolobii and to compare it with the sheathed flagella which are known to occur in a very few genera of Gram-positive and Gram-negative bacteria. Organisms not to be treated with reagents were carried through two 72 hr serial subcultures in Craigie tubes of motility medium and 5 or 8 serial subcultures of variable duration in 6 x 3 in., tubes containing 5 ml. peptone yeast extract broth.Organisms to be treated with various reagents (including distilled water controls) were

Bacteria which cause pink disease of pineapple, identified on the basis of their nutritional and biochemical activities, were found to belong to three genera. These bacteria include the following species: Gluconobacter oxydans, Acetobacter aceti, and Erwinia herbicola. Several pink disease strains required one to three vitamins for growth. Both G. oxydans strains 303D and 180 required biotin, nicotinic acid, and pantothenic acid for growth; E. herbicola 189 required only nicotinic acid; however, A aceti 295 was able to grow without any added supplements in glucose mineral salts medium. Optimal vitamin concentrations for maximal growth and optimal pH for the maximal number of generations per hour was established for a few pink disease strains.