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Bacterium CP-1 isolated from Scottish waters is an aerobic prokaryote with a high guanine:cytosine ratio (68%), which causes lysis of a variety of blue-green algae. When suspensions of algae and bacteria are mixed the bacteria can be seen to glide towards the algae where they become attached end-on round the algal cells. There is evidence that the bacteria produce substances at the point of contact with the algae which are necessary for algal lysis to occur. Lysis of vegetative cells may occur within 30 minutes of the bacteria becoming attached. Heterocysts do not lyse in this way although their intracellular contents may eventually degenerate. When vegetative cells rupture, the protoplasmic contents, including gas vacuoles when present, are released and empty-looking 'ghosts' which retain the original cell shape may remain for a time although these too eventually break down. There is some evidence that the mode of filament lysis may be random, intercalary or terminal. At the ultrastructural level the initial effect of CP-1 is to cause lysis of the L[SUB2] layer of the algal cell wall and this effect is similar to that obtained using lysozyme. This is followed by rupture or disintegration of the other cell wall layers, and 'scroll' -like structures, either of coiled up cell wall material (Microcystis) or of the plasmalemma (Nostoc) may be found scattered throughout the preparations of lysed cells. In fully lysed cells there is a loss of polyphosphate bodies, structured granules, gas vacuoles, and most other cellular inclusions. Released gas vesicles can be collected from the surface of the solution of lysed cells, and there is evidence that these vesicles may fracture easily near the conical ends. In fully lysed cells, the thylakoid membranes remain, often with wide lumens between. This thylakoidal system is contorted and branched, ramifies through the cell and shows constrictions of the membrane system at intervals. [ABSTRACT FROM AUTHOR]

Of thirty-six species of metabolically active lichens taken mainly from Scottish coastal habitats, eight showed a capacity to reduce acetylene to ethylene. These were species of Collema Web., Lichina C. Ag., Peltigera Willd. and Placopsis Nyl. and all contained a blue-green alga as the primary or secondary phycobiont. Acetylene reduction rates were sometimes high in the field and showed marked diurnal and seasonal variations. Nitrogenase activity was higher in vegetative than in fruiting thalli of Peltigera rufescens, and in P. canina was higher nearer the apices of the thalli than in older parts. Of the environmental factors affecting fixation, desiccation was the most important, temperature was less important and the lichens, while requiring light, could continue to fix nitrogen in the dark for up to i8 hours (Lichina confinis) and 26 hours (Peltigera rufescens). The average percentage nitrogen contents of nitrogen-fixing lichens (2.20%) was significantly higher than the non-nitrogen-fixing lichens (0.83%). The maximum and mean fates of nitrogen fixation by P. rufescens were 38.1 and 4.1 μg N (mg N)[SUP-1] day[SUP-1] respectively. The corresponding values for Lichina confinis were 29.4 and 0.4. [ABSTRACT FROM AUTHOR]

Four bacterial isolates have been obtained which cause lysis of laboratory cultures and natural populations of blue-green algae. Over forty algal strains belonging to all orders of the blue-green algae and including bloom-forming species are susceptible. The bacteria also lyse certain gram-positive and gram-negative bacteria. The organisms are aerobic, gram-negative rods, aflagellate, motile and pigmented with an absorption maximum of the pigments in methanol occurring at nm and with shoulders at 460 nm and 415 nm. The guanine and cytosine in the DNA is within the range of 65-69±1 M%. The organisms are identified tentatively as members of the Myxobacterales. Lysis of vegetative cells of the algae depends on the presence of growing bacteria, bacteria-free filtrates alone being insufficient to cause lysis. Heterocysts are not lysed. The bacterial plaques resemble viral plaques in appearance. The lytic agents rapidly inhibit metabolic activity of the susceptible algae and may cause cell lysis within 2-10 hours. The isolates can be propagated readily in the absence of the host and are probably widely distributed in freshwater habitats. [ABSTRACT FROM AUTHOR]

Nitrogen fixation in various Wisconsin lakes was compared using the C[sub2]H[sub2] reduction technique. Rates of C[sub2]H[sub2] reduction were unaffected by N[sub2] when sufficient C[sub2]H[sub2] was added to the gas phase. Thus in field studies the natural gas phase need not be removed before the addition of C[sub2]H[sub2]. C[sub2]H[sub2] was reduced rapidly in eutrophic waters (Little Arbor Vitae Lake, Lake Mendota and southern Green Bay) but more slowly in oligotrophic waters (Crystal Lake, Trout Lake, Lake Mary and northern Green Bay). C[sub2]H[sub2] reduction was greatest in the surface waters, was largely light-dependent and showed a marked diurnal variation. There was also significant variation with area and with time, and in general acetylene reduction was detected only when heterocystous algae were present. The rate of nitrogen fixation in Lake Mendota, calculated on the basis of weekly measurements taken during most of the ice-free season, was approximately 2.4 kg/ha/year. [ABSTRACT FROM AUTHOR]

A virus which is pathogenic to certain blue-green algae belonging to the genera Plectonema, Phormidium and Lyngbya has been isolated from a variety of freshwater habitats in Scotland and has been detected over a 12-month period in one of these habitats. The virus (D-1) is a cyanophage, has an isohedral head and a short tail and is morphologically and serologically related to the LPP-1 virus isolated from the United States and the G111 virus isolated from Israel by other workers. The partially purified virus has an absorption spectrum characteristic of a nucleoprotein with a maximum at 260 nm and a minimum at 243 nm. D-1 is temperature sensitive being inactivated on heating at 60° C for 6 minutes. Its multiplication rate is fast, increasing from an initial titre of 10[SUP3] to 10[SUP12]PFU/ml within 40 hours. The lysis of the host cell results in a rapid loss of the phycobilin and chlorophyll pigments. [ABSTRACT FROM AUTHOR]