Poly-β-hydroxybutyrate production in eight strains of the genus Acinetobacter

Since poly-β-hydroxybutyrate (PHB) inclusions have been reported in only a few strains of Acinetobacter grown on β-hydroxybutyrate, it was of interest to study comparatively the production of this lipid reserve in eight different acinetobacters. Three lines of evidence for PHB production were used: spectrophotometric analysis, infrared analysis, and electron microscopy. The spectrophotometric method showed that all eight strains produce PHB in stationary phase, the amounts ranging from 0.55 to 10.7 fmol/cell. PHB production was maximum after 1 h of growth in batch culture, with the amounts declining by 2 h and returning to near stationary phase cell levels in 4 h. Infrared spectra of purified PHB from the eight strains matched the spectrum of a commercial sample of PHB. In electron micrographs, the PHB reserves were visible as small electron-transparent bodies delineated by ultramembranes. PHB production in four strains (bath cultures) varied in response to exogenous glucose or xylose, with maximum production occurring over a range of 8–17 mM monosaccharide. Glucose was transported into cells by all strains in amounts that ranged from 0.5 to 1.6 fmol/cell, and 0.1–2.2% of that glucose was converted into PHB. Glucose transport was inhibited by cyanide. Key words: poly-β-hydroxybutyrate, acinetobacters.

Ultrastructure of the infection of spruce budworm larvae by the fungus Entomophaga aulicae

The infection of spruce budworm larvae by the fungus Entomophaga aulicae was studied by light, scanning, and transmission electron microscopy. Exposure of the larvae to conidia resulted in the death of the host and the production of a crop of infective conidia within 5 to 6 days. Germinating conidia produced appressoria prior to penetration of the larval cuticle. Nuclei in appressoria were larger and contained less heavily condensed chromatin than nuclei in other stages of fungal development. Attachment and infection were characterized by distinct changes in the wall layers of the fungus. An infection hypha grew through the insect tissues directly into the hemocoel where discontinuities were observed in the wall layers at the apex of the infection hypha. These discontinuities are probably associated with protoplast formation in vivo. Protoplasts with polysaccharide and lipid storage material were present in the hemolymph of larvae 3 days after exposure to conidia. Thick-walled hyphal bodies with abundant lipid reserve filled the larval body cavity by the 5th day. Hyphal bodies germinated to produce unbranched, aseptate conidiophores which emerged through the host cuticle prior to conidiogenesis.

Energy Metabolism in a Rapidly Developing Marine Fish Egg, the Red Drum (Sciaenops ocellata)

Rates of utilization of different lipid classes, glycogen, protein, and adenine nucleotides in the eggs of red drum (Sciaenops ocellata) were measured concurrently throughout embryonic development. Red drum eggs are small, pelagic, and very rapidly developing, going from fertilization to hatching in as little as 19 h at natural spawning temperatures. Wax esters comprised about 50% of the neutral lipid reserve along with triglyceride. Lipid was quantitatively the most important energy reserve supplying virtually all of the catabolic demand. Total lipid content decreased 30% from 23.6 to 16.6 mg/g during development. Glycogen decreased 53% from 0.279 to 0.103 mg/g. Protein did not contribute to catabolism. Total adenylates, primarily ATP, decreased from 564 to 271 nmol/g. Adenylate energy charge decreased from 0.87 to 0.58. Glycogen and lipid were used concurrently rather than sequentially during development. The rapid rate of development could be accounted for by simple thermal effects on metabolism rather than any unique biochemical adaptation. High concentrations of wax ester may be an adaptation for maintaining buoyancy at reduced salinities.

Studies on hyphal development and appressorium formation of Colletotrichum graminicola

The fine structure of actively growing hyphae of Colletotrichum graminicola was investigated. The hyphae were found to secrete a mucilaginous sheath into which melanizing particles and fibrils were deposited. Classical ubiquitous mitochondria, multipored doublewalled nuclei, ribosomes, mesosome-like structures, lomosomes, vacuoles, and inclusions such as lipids, closely associated with vacuoles, especially noticeable during germination, as well as glycogen were present. During maturation, vacuoles appeared and enlarged. In addition, a few endoplasmic reticulum profiles were observed in actively growing hyphae. Mitochondrial profiles changed from spherical to elongate. A plasmalemma, perhaps double in nature, was present. Penetration of one hypha by another was also observed.The mature appressorium exhibited a thick three-layered cell wall. This thick wall appeared to play a part in poor fixation and embedding, resulting in a poor definition of such cellular organelles as ribosomes, nuclei, etc. Internally, appressoria, depending on the stage of development, exhibited many vacuoles and osmiophilic deposits indicative of lipid reserve material. A germ pore through which a germ tube and migrating organelles and cytoplasm emerged was also observed.

Seasonal variations in biochemical composition during the reproductive cycle of the intertidal gastropod Thais lamellosa Gmelin (Gastropoda, Prosobranchia)

Seasonal variations in biochemical constituents of Thais lamellosa Gmelin in relation to the reproductive cycle were studied. Digestive gland, foot muscle, and gonad were analyzed for protein, glycogen, lipid, and ash for 1 year. Data on feeding and gamete maturation were obtained from histological sections of digestive gland and gonad. Major periods of feeding activity occurred in April and August. The spawning peak was in March and gametogenesis began in July. Maximum glycogen levels coincided with major feeding periods but reserves in the digestive gland were mainly lipid. This lipid reserve was used during the winter. Glycogen was at a relatively low level in all tissues and appeared to be used by the developing gonad. The foot muscle stored neither lipid nor glycogen to any appreciable extern.During winter the digestive gland index decreased as reserves were used. The ovary index held constant from October to February then dropped sharply with spawning. Animals kept for the same period under artificial summer conditions showed no decrease in the digestive gland index, but a decrease in the ovary index. Few oogonia reached maturity and many were resorbed. Starved animals used more protein from the ovary than fed animals.