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Merrick, J. M. (State University of New York, Buffalo), D. G. Lundgren, and R. M. Pfister. Morphological changes in poly-beta-hydroxybutyrate granules associated with decreased susceptibility to enzymatic hydrolysis. J. Bacteriol. 89:234-239. 1965.-A complex enzyme system obtained from extracts of Rhodospirillum rubrum cells hydrolyzes poly-beta-hydroxybutyric acid (PHB) contained in native PHB granules isolated from Bacillus megaterium. A labile factor associated with the granules and necessary for depolymerization is easily destroyed by various chemical and physical treatments. Granules inactivated by these treatments were examined in an electron microscope. In all cases, the distinct morphological appearance of native granules was altered. Morphological changes were mainly characterized by membrane fragmentation, loss of coalescence, and surface alterations. These observations suggest that native PHB granules possess definite structural features, disruption of which results in decreased susceptibility of the polymer to enzymatic hydrolysis.

The structure of the cell wall, the arrangement of the cyst exine, and the origin and distribution of intine vesicles in Azotobacter vinelandii ATCC 12837 were examined by freeze-etching and conventional electron microscopic techniques. In the vegetative organism the cell wall appears to have a woven texture which disappears during cyst formation. The exine is composed of two different types of material: the outer layer is a fibrous, amorphous layer, and the numerous inner layers form the basic hexagonal structures which unite to form the cyst coat. The presence of intine vesicles in the encysting organism was confirmed in frozen-etched cells. The appearance of frozen-etched cells and cysts and the distribution of capsular material indicate that extracellular polysaccharide is an important factor in cyst formation.

Pfister, Robert M. (Lamont Geological Observatory, Palisades, N.Y.), and Paul R. Burkholder. Numerical taxonomy of some bacteria isolated from Antarctic and tropical seawaters. J. Bacteriol. 90:863-872. 1965.-Microorganisms from Antarctic seas and from tropical waters near Puerto Rico were examined with a series of morphological, physiological, and biochemical tests. The results of these analyses were coded on punch cards, and similarity matrices were computed with a program for an IBM 1620 computer. When the matrix was reordered by use of the single-linkage technique, and the results were plotted with four symbols for different per cent similarity ranges, nine groups of microorganisms were revealed. The data suggest that organisms occurring in different areas of the open ocean may be profitably studied with standardized computer techniques.

Several gram-negative, polarly flagellated rods were isolated on the basis of their flocculent growth habit. Some of the isolates possessed a capsular matrix which is composed of exocellular fibrils. Other isolates did not appear to have a capsular matrix when examined with a bright-field microscope with or without the aid of stains. However, these latter type isolates did possess exocellular material which can be demonstrated by adsorption of a fluorescent dye under an ultraviolet microscope. Electron microscopic examination demonstrated that the exocellular material around all isolates examined is fibrillar. The fibrils were susceptible to cellulase although all fibrils did not appear to be identical. It is postulated that the exocellular polymers were responsible for the flocculent growth habit of the bacteria, and that the process of bacterial flocculation produced by synthetic polyelectrolytes was essentially the same as that caused by naturally produced exopolymers.

Five gram-negative bacteria, two gram-positive bacteria, and one yeast were isolated from "acid streamers" taken from acid mine water. One gram-positive rod which has been tentatively identified as a Bacillus species appeared to be the predominant organism in the streamers. This isolate produced copious amounts of extracellular polymer at 10 C in the laboratory and was considered to be the primary source of polymer in the "acid streamer" slime matrix. The organism grew slowly at pH 2.8 in mine water media, but the optimal pH was approximately 7.0.

The fingerlike projections, which have been considered to be characteristic of the genus Zoogloea, appear to consist of generally globular packets of cells, each surrounded by capsular matrix. The individual packets which surround Z. ramigera 115 cells appear to adhere one to another by intermeshed fibrils that measure 2 to 5 nm in diameter. The fibril polymer appears to be polyglucose that is susceptible to cellulase. The polymer resembles cellulose in several respects, with the exception that it is soluble in 1 n NaOH. Although Z. ramigera I-16-M does not possess an observable zoogloeal matrix when viewed under a light microscope, chemical data indicate that it does produce cellulase-susceptible polymer. Fibrils can be observed under the electron microscope, which are resistant to 1 n NaOH and may be cellulose. Less polymer fibrils are observed around isolate I-16-M cells than around isolate 115 cells; the inability to observe the I-16-M material as a zoogloeal matrix under light microscopy may be due to lack of sufficient amount of polymer.

"Acid streamers" found in acid coal mine drainage consist of bacteria trapped within an extracellular fibrillar polymer network. Inorganic compounds also precipitate within the polymer network. Several bacteria which appear to be different and are presumed to be different species are associated in the slimy mass of the "acid streamers." The "streamers" contain individual microcolonies or microcosms that can be recognized by a selective polysaccharide stain, which suggests that the slime streamer is a conglomeration of polymers produced by more than one species.