EXTRACELLULAR INVESTMENTS IN BLUE-GREEN ALGAE WITH PARTICULAR EMPHASIS ON THE GENUS NOSTOC1

The investments of a wide variety of blue-green algae were examined. Many strains formed diffuse slime layers that were unnoticed unless mounted in India ink. Slime occurred in species with and without readily detectable sheaths. The extracellular integument type seemed consistent within strains, although the extent often varied with culture conditions. Experiments with NOSTOC on agar plates indicated that motility was inversely related to the amount of slime present. Some aspects of behavior were related to the nature of an alga's investment.     

ULTRASTRUCTURAL OBSERVATION OF CROSSWALLS IN THE BLUE-GREEN ALGA SPIRULINA MAJOR1,2

Spirulina major Kütz. was observed with the electron microscope and compared at the ultrastructural level with a species of Arthrospira. The presence, of crosswalls which develop by progressive ingrowth from peripheral walls was demonstrated in S. major. Since cellular septation is not consistent with the generally accepted characters of the genus Spirulina, a taxonomic shift may be indicated.     

FREQUENT HETEROCYST GERMINATION IN THE BLUE-GREEN ALGA GLOEOTRICHIA GHOSEI SINGH1

A unique feature, frequent heterocyst germination, has been observed in a nonsporulating mutant clone (of spontaneous origin) of the blue-green alga Gloeotrichia ghosei Singh. The controlling factor seems to be the presence of ammoniacal nitrogen in the medium. In addition, such a medium supports differentiation of successive crops of new heterocysts and their germination in the name medium and in the same algal culture. Contrary to previous observations with oilier blue-green algae, ammoniacal nitrogen does not seem to inhibit heterocyst differentiation in this alga. Both the parent alga and its mutant clone grow poorly in a nitrogen-free medium, which, although they are not completely free from bacteria, may indicate that they tire poor fixers or nonfixers. However, they form a large number of heterocysts under these conditions. The general conclusion is that the heterocysts of blue-green algae show a multiplicity of structure and function. In the present case they have reproductive function leading to direct propagation of the alga. The bearing of these findings on the interrelationships of the genera Gloeotrichia and Rivularia has been discussed. It has been concluded that the distinction between them is purely artificial.     

COMPLEMENTARY CHROMATIC ADAPTATION IN A FILAMENTOUS BLUE-GREEN ALGA

Fluorescent and red light environments generate greatly different patterns of pigmentation and morphology in Fremyella diplosiphon. Most strikingly, red-illuminated cultures contain no measurable C-phycoerythrin and have a mean filament length about 10 times shorter than fluorescent-illuminated cultures. C-phycoerythrin behaves as a photoinducible constituent of this alga. Spectrophotometric and immunochemical procedures were devised so that C-phycoerythrin metabolism could be studied quantitatively with [¹⁴C]-phenylalanine pulse-chased cultures. Transfer of red-illuminated cultures to fluorescent light initiates C-phycoerythrin production by essentially de novo synthesis. C-phycoerythrin is not degraded to any significant extent in cultures continuously illuminated with fluorescent light. Transfer of fluorescent-illuminated cultures to red light causes an abrupt cessation of C-phycoerythrin synthesis. The C-phycoerythrin content of cultures adapting to red light decreases and subsequently becomes constant. Loss of C-phycoerythrin is not brought about by metabolic degradation, but rather by a decrease in mean filament length which is effected by transcellular breakage. In this experimental system, light influences intracellular C-phycoerythrin levels by regulating the rate of synthesis of the chromoprotein.     

CYTOLOGY OF BLUE-GREEN ALGAE. I. THE CELLS OF SYMPLOCA MUSCORUM

Pankratz , H. S., and C. C. Bowen . (Iowa State U., Ames.) Cytology of blue-green algae. I. The cells of Symploca muscorum . Amer. Jour. Bot. 50(4): 387–399. Illus. 1963.—The cellular morphology of Symploca muscorum is described, based upon electron micrographs utilizing improved techniques of specimen preparation. Except for a limiting plasma membrane, ribosomes, and Feulgen-positive chromatin, the cells have little resemblance to those of higher organisms. The longitudinal components of the cellular envelope consist of a 200–300 mμ fibrous sheath and a complex inner investment about 35 mμ thick which includes at least 3 distinctly layered wall elements in addition to the typical 7-mμ unit membrane forming the plasma membrane. A row of very small elongate “pores” pierce the inner investment on each side of, and immediately adjacent to, the junction of the longitudinal walls and the crosswalls. Crosswalls vary in thickness from 3 to 20 mμ, depending upon their age, and arise as elaborations of the inner layers of the longitudinal inner investment. The photosynthetic lamellar component of the cytoplasm consists of flattened sacs formed from unit membranes. The lamellae are concentrated in the peripheral region of the cell and usually are parallel to the longitudinal wall. These often extend from one crosswall to the next but, except for a few cases, are not continuous with the plasma membrane at either end. The Feulgen-positive nucleoplasm appears as an anastomosing system of lightstaining regions containing fibrils 2–5 mμ in diameter. The morphology and interrelationship of a number of other cellular elements are described: (1) structured granules range up to 0.5μ in diameter and occur near crosswalls; (2) polyhedral bodies, 0.2–0.5μ in diameter, are closely associated with the nucleoplasm; (3) “cylindrical bodies” characteristically consist of 2 concentric cylinders, are about 13 mμ in diameter and up to lμ in length; (4) “α granules” are spherical or somewhat elongate elements about 30 mμ in diameter and characteristically associated with the photosynthetic lamellae and structured granules; (5) “β granules” are spherical, highly osmiophilic granules which range from 30 to 90 mμ in diameter; (6) ribosomes, 10–15 mμ, in diameter, are most numerous near the nucleoplasm; (7) plasmodesms penetrate the crosswalls between adjacent cells. The cells of this organism can best be described as being in a “steady state” of division, and there is no evidence of any kind of organized distribution of the nucleoplasm to daughter cells during the constant progress of cytokinesis.     

EVIDENCE OF A ROLE OF HETEROCYSTS IN THE SPORULATION OF A BLUE-GREEN ALGA

Sporulation of vegetative cells adjacent to heterocysts is prevented by detachment of the two cell types, probably without impairment of the capacity of those vegetative cells to sporulate. Apparently, therefore, heterocysts are in part responsible for the sporulation of vegetative cells attached to them.     

柱胞鱼腥藻原生质球自发融合的研究

早在1976年,细菌就实现了原生质体融合杂交[1]。同样是原核生物,蓝藻原生质球融合及细胞杂交至今没有任何报道。究其原因,首先是由于蓝藻原生质球再生技术长期不过关、近年来,蓝藻原生质球再生虽有若干报道[2～4],但再生技术还不够成熟;另一方面,很早就通过电镜检查发现     

GLIDING MOTILITY IN THE BLUE-GREEN ALGA OSCILLATORIA PRINCEPS1

Gliding is an active movement displayed by a microorganism in contact with a solid substrate where there is no evidence of a motility organelle or of a conformational change in the organism. Gliding may be accompanied by rotations, reversals, flectional activity, and mucilage sheath production, as well as linear translation. Previous explanations of the mechanism responsible did not consider all these aspects of behavior. The gliding behavior and ultrastructure of the blue-green alga Oscillatoria princeps Vaucher were examined. O. princeps has a maximum observed gliding rate of 11.1 μm/sec. The trichomes can glide in either longitudinal direction following rapid and occasionally frequent reversals. Right-handed trichome rotation was always observed, which means that any surface point on these trichomes traces a 60-deg right-handed helix. A mucilage sheath envelopes the moving trichomes. The rate of gliding was reduced by viscous substrates, extreme pH, lysozyme, DNP, and cyanide, while sustained darkness had no inhibitory effect. Ultrastructurally, the cell wall is composed of an L-1 layer which is 10 nm thick and often ill-defined. The L-2 layer which is outside this is 200 nm thick and participates in septum formation. The L-3 layer is outside the L-2 and is continuous over the trichome surface. The L-4 “membrane” lies outside the L-3 layer. Grazing surface sections and freeze-etch replicas show a parallel and tight array of 6–9 nm wide continuous fibrils in the cell wall on the surface of the distinctive L-2 layer. Isolated wall fragments were tightly coiled inside out with the fibrils on the inside. The angle of orientation for the fibrils was to the right in a helix with a pitch of 60 deg. O. animalis, a blue-green alga with a movement tracing a left-handed helix, showed a similar array of fibrils oriented in a left-handed helix with a pitch of 60 deg. It is proposed that gliding is produced by unidirectional waves of bending in the fibrils which, act against the sheath or substrate, tints displacing the trichome.     

ENERGY EXPENDITURE FOR GLIDING MOTILITY IN A BLUE-GREEN ALGA1

The energy required to overcome viscous drag in a gliding trichome of a blue-green alga advancing and rotating through a medium of known viscosity (67 poise at 25 C) has been calculated to be about 0.05% of the energy available from oxidative phosphorylation (based on respiration measurements), whereas 0.2–5% are possible figures for the amount actually expended. These values represent a low energy demand for a function of probable high survival value, but are comparable to estimates for motility in flagellated cells.