The benthic filamentous cyanobacteria Phormidium J-1 and Anabaenopsis circularis 6720 adsorbed suspended clay particles and coflocculated with them. Coflocculation was correlated with production of extracellular flocculants. In old cultures there was a decrease in both coflocculating activity and cell surface hydrophobicity. It is proposed that attachment to the benthos is facilitated by the common action of both coflocculation and hydrophobic interactions. A simultaneous decrease in these two surface characteristics enables the cells to detach and colonize new surfaces.

Nitrogen transformation was examined in the sequential stages of wastewater treatment in the Dan Region Wastewater Reclamation Project in Israel. It was shown that volatilization, assimilation and nitrification were the mechanisms responsible for ammonia removal from the water during various treatment stages. When the recharge basin dried, nitrification occurred, leading to removal of ammonia and accumulation of nitrate in the sand. Upon flooding the recharge basin nitrate was leached from the sand and accumulated in the groundwater, while ammonia was adsorbed to particles in the sand layers.

Various axenic strains of Microcystis aeruginosa were found to have different short term toxic effects on Daphnia magna. One of these toxic manifestations, the “blocking” effect, markedly reduced the food uptake by the daphnids. In addition, several of the Microcystis strains are lethal for juvenile and adult daphnids. No correlations were found between the blocking of ingestion, lethality to daphnids, and the “mouse‐killing” factors of Microcystis. Thus, several toxic principles are responsible for the different short term toxic manifestations.

To simulate the occurrence of bacterial and algal blooms in the Dead Sea, we filled 5.6 m3 outdoor ponds with mixtures of Dead Sea water and Mediterranean water, at different seasons, and studied the effect of salinity and of addition of glycerol, glucose and different concentrations of phosphate on the rate and extent of bacterial and algal growth. Addition of phosphate appeared to be essential for the development of mass blooms of both the green alga Dunaliella and of the red halobacteria. In the presence of phosphate the growth rates were high only when the Dead Sea water was diluted by at least 25–35% with Mediterranean water. Also, at low temperatures (14–17°C) mass blooms of bacteria and algae occurred, but growth rates were reduced, and the maximal salinity at which growth was observed shifted to a lower value. Glucose, glycerol and a Dunaliella bloom all proved to be suitable carbon sources for mass development of halobacteria.

Log phase endosymbiotic diatom species, Nitzschia valdestriata, N. laevis, N. panduriformis var. continua, N. frustulum var. subsalina and var. symbiotica, Amphora tenerima, Fragilaria shiloi and Navicula hanseniana, were aseptically exposed to an homogenate of freshly crushed foraminiferal host species (Amphistegina). To various degrees, depending upon endosymbiont species, the host homogenate affected the formation of new frustules of growing and dividing cells. F. shiloi was the most affected species. New cells were spheroids and had only vestiges of frustules or none at all. Fewer numbers of the other species tested (40 to 60%) were abnormal. The raphe and keel of affected Nitzschia spp. were usually curved and incomplete. Many cells were spherical. We infer that “host substances” are probably responsible for the maintenance of the frustule-less state in vivo and that if ingested potential endosymbionts escape digestion, they could become frustule-less after growth and cell division. Host homogenate also increased the levels of photosynthetate released by diatoms to their medium. N. valdestriata was stimulated to release 76% of its photosynthetate while other species tested were stimulated to release between one quarter to one half of their photosynthetate. Host homogenate was also effective in causing the release of 43% of the photosynthetate of a free-living diatom, Amphora sp., which was also tested in the experiment. The concentration of the metabolites released in the experiment was too low for us to identify by TLC.

A bloom of the unicellular green alga Dunaliella parva in the Dead Sea is described, and physicochemical factors triggering its rise and decline are analyzed. The bloom developed in summer 1980, reached population densities of up to 8,800 cells·ml−1, and gradually declined until finally collapsing during the first months of 1981. Algal development was limited to a thin layer of less saline water floating on top of the heavy brines. Laboratory experiments showed that both dilution of Dead Sea water and increase in phosphate concentration are required for algal development in the Dead Sea.The Dunaliella community followed the deepening of the pycnocline to depths of 15–25 m in September–October 1980, with resultant light limitation to part of the population and cell death by starvation in the absence of light. The inflow of new floodwaters generated a new pycnocline which may have prevented the cells below from reaching the euphotic surface layer, resulting in the death of most of the remaining population.

A critical reappraisal of our knowledge on the photosynthetic communities of the open oceans and large lakes, and the development of new approaches to measurement of their activity in situ have greatly influenced our present views on the structure and function of these communities. Based on the accumulated knowledge of the physiology and molecular biology of the photosynthetic organisms involved we can now understand some of the mechanisms underlying adaptive processes operative in Nature. The distribution pattern of the photosynthetic communities in the photic zone of aquatic ecosystems is controlled by the nature of the photosynthetic apparatus, the range of antenna pigments formed by the different organisms, and their ability to regulate quantitatively and qualitatively pigment synthesis in response to light intensity and spectral composition. An additional factor controlling distribution is the ability of many of the photosynthetic organisms to escape the oligotrophic conditions prevailing in the water column by adherence to interfaces such as the benthos or the neuston. A major factor governing the ability of organisms to adhere to these interfaces is the hydrophobicity of their cell envelope. Planktonic organisms, on the other hand, have highly hydrophilic envelopes. Benthic organisms have evolved mechanisms for dispersal, which in many cases involves the formation by the hydrophobic adherent parent cells of hydrophilic progeny cells. This has been confirmed for several hormogonia-producing cyanobacteria. Benthic photosynthetic organisms must in addition be capable of phototactic motility and have versatile metabolic patterns to adapt to the rapid fluctuations in their environment. The photosynthetic organisms of the neuston and the cyanobacteria that form surface scum share mechanisms enabling the cells to withstand conditions of photo-oxidation, lethal to most non-resistant organisms.

Aquatic ecosystems include the two extremes: constant environmental conditions in the main bodies of water, and unstable fluctuating conditions in the shallow margins of the aquatic ecosystems. Aquatic microorganisms living in the main oceans can thus be characterized by a single prototype being moderately halophilic, psychrophilic, to some extreme barophilic and all must be oligotrophs managing to survive and multiply in extremely low nutrient concentrations. On the other hand those populating the shallow margins must be adapted to rapidly fluctuating environments and thus have multipotential metabolic patterns. Oscillatoria limnetica can serve as a model for this being capable of shifts from oxygenic to non-oxygenic photosynthesis, having multiple dark energy generating systems, fixing nitrogen anaerobically and capable of induction of resistance mechanisms to overcome oxygen toxicity.

Luminous bacteria in the Mediterranean Sea and the Gulf of Aqaba-Elat have different distribution patterns. In the Mediterranean Sea, Beneckea harveyi is present all year round, with different subtypes alternating in summer and winter; Photobacterium fischeri was only present during the winter. In the Gulf of Elat, P. leiognathi is present throughout the water column in similar densities during the entire year. This constancy in distribution is presumably due to the near-constancy in water temperature. In summer, Photobacterium leiognathi is replaced by B. harveyi in coastal surface waters. In the hypersaline Bardawil lagoon, only B. harveyi types are present. P. fischeri , a major component of the Mediterranean Sea winter communities, is absent from the lagoon. Luminous Beneckea strains show a great diversity in properties, e.g. temperature range for growth, sensitivity to infection by phages, sensitivity to attack by Bdellovibrio strains, and differences in tolerance to high-salinity shock. Therefore, subdivision of the taxonomic cluster of B. harveyi into subtypes is indicated. The composition of the luminous bacteria communities may serve as indicators of different marine water bodies. The symbiotic luminous bacteria of the light organ of the common Gulf of Elat fish, Photoblepharon palbebratus steinitzi , is different from any of the types described.

Physiological characteristics of luminous bacteria isolated from the Mediterranean and Gulf of Elat were compared to determine their relationship to the specific seasonal and geographic distribution patterns of these bacteria. The effects of temperature on growth rate and yield, relative sensitivity to photooxidation, resistance to high salt concentration (8%), and ability to grow in nutrient-poor conditions appear to control these patterns. The winter appearance of Photobacterium fischeri and the succession of winter and summer types of Beneckea harveyi in the eastern Mediterranean are explained by different temperature requirements for growth. Sensitivity to photooxidation explains the disappearance of P. leiognathi , present in the main body of the Gulf of Elat throughout the year, from the shallow coastal strip. B. harveyi is present in this coastal strip which is higher in nutrients and in productivity than the open waters. Competition experiments between B. harveyi and P. leiognathi in batch and continuous culture indicate that the oligotrophic P. leiognathi is outcompeted by B. harveyi in rich and even in relatively poor media. The distribution pattern found in the Bardawil hypersaline lagoon is explained by selection of salinity-resistant mutants of B. harveyi from the Mediterranean Sea.

Using a novel method for selecting mutants resistant to photooxidation a highly resistant mutant of the blue-green alga (cyanobacterium) Plectonema boryanum was obtained and its behaviour under photooxidative conditions was studied in comparison with sensitive strains. This mutant, designated PBstr LR-1, grown organotrophically, contained 40–50% less phycocyanin and chlorophyll per mg protein than the light-grown wild type cells. A pigment absorbing between 455 nm and 490 nm was detected in an aqueous extract of the mutant cells which was absent in extracts of wild type cells. An analysis of the ratio of superoxide dismutase (SOD) isoenzymes revealed that in the photooxidation resistant mutant, the major component of SOD is due to a hydrogen peroxide insensitive isoenzyme, while in the wild type and other sensitive strains, the majority of the SOD activity was due to a hydrogen peroxide sensitive isoenzyme. The significance of these finding, in terms of mechanisms protecting against photodynamic action is discussed.

Marine bdellovibrios show a specific requirement for K + , Ca 2+ , and Mg 2+ . Potassium is essential for high velocity and seems to be necessary for attachment of the free bdellovibrios. Calcium and magnesium are necessary for attachment and penetration. Magnesium also plays a role in maintaining the integrity of the bdelloplast. The adaptation of these bdellovibrios to the marine environment is manifested by their stringent cation requirements.

The relations between photosynthetic and nonphotosynthetic (chemoorganotrophic and chemolithotrophic) microorganisms in Solar Lake were studied during the annual limnological cycle. Six different bacterial plates were observed during stratification by direct and viable bacterial counts, light and dark CO2 incorporation, chlorophyll a, protein, ATP, and ETS determinations. A maximal dark CO2 incorporation of 1,014 mg C m−3 d−1 may represent as much as 16,900 mg C m−3 d−1 of chemoorganotrophic bacterial production, on the assumption that these bacteria assimilate an average of 6% CO2 of their total carbon uptake. This calculated production is very high in comparison to the recorded photosynthetic maximum of 4,960 mg C m−3 d−1. The organic carbon needed for such a high chemoorganotrophic production may be supplied by the benthic cyanobacterial mats. Extremely high specific activities of ATP and ETS for the layer immediately above the thermocline indicate a very active bacterial plate at this layer.

Cyanobacterial mats of Solar Lake, studied in the field and by microscopic methods, are classified into four types: flat shallow‐water mat, pinnacle mat on the upper slope, cyanobacterial and other photosynthetic bacterial films on the lower slope, and flocculose mat at the bottom. The annual cycle and development of the four types are described. Measurements of photosynthesis by the flat shallow‐water mat in the field and the laboratory yielded an average value of 10 g C m−2 d−1. In the flocculose anaerobic bottom mat 5 g C m−2 d−1 was measured. Total accretion rates including organogenic material for the four mat types range between 5 and 50 cm 100 yr−1; aerobic and anaerobic degradation of the organic production of the shallow‐water mat remineralizes more than 99% of the biomass. In the deeper parts of the mat, organic matter is transformed into carbonates. The role of bacteria in this process is demonstrated by ultramorphological analyses and by comparison to laboratory experiments with bacterial isolates.

Cyanophage LPP1G is reproduced at the same yield in heterotrophic conditions (dark, glucose) as in photoautotrophic conditions; aerobiosis is required for dark cyanophage replication. Exogenous glucose is not required for the cyanophage replication in the dark in heterotrophically grown cells. In photoautotrophically grown cells, the maximum burst size in dark and glucose is delayed for a period corresponding to glucose uptake induction. Cyanophage LPP2SPI replication occurs in conditions where only Photosystem I operates. Of photosynthesis parameters tested, only CO2 photoassimilation is affected during cyanophage LPP1G infection under photoautotrophic conditions.

Photodynamic effects were demonstrated and assayed under field conditions in a number of different laboratory strains and pond isolates of cyanobacteria; parameters assayed for resistance to photooxidation were viable count, turbidity of the cyanobacterial suspension, and protein and pigment contents. The effects of density, colonial structure, and internal gas vacuoles on the lethal outcome were investigated. The stability and formation of superoxide dismutase under photooxidative conditions in the field and laboratory were studied in the different strains. An isolate of Microcystis from blooms in ponds exhibited extremely high resistance to photooxidation, which was abolished by exposure to chloramphenicol.

Marine bdellovibrio isolates from the Israeli littoral of the Mediterranean Sea were screened and characterized in terms of host range, temperature and salinity ranges, cation requirement, mutation frequency, and G + C% mole content. Ten types of isolates were distinguished on the basis of these parameters.

PROFOUND differences in structure and function separate the prokaryotic cyanobacteria (blue-green algae) from eukaryotic algae and plants, whereas oxygenic photosynthesis is considered to distinguish the cyanobacteria and eukaryotic plants from the other phototrophic bacteria. The prevailing concepts on the cyanobacteria emphasise their prokaryotic nature and oxygenic photosynthesis. This combination of properties, among others, led to the suggestion that the cyanobacteria represent a group of possible progenitors of chloroplasts1. While cyanobacteria typically exhibit oxygenic photosynthesis with two photosystems using electrons from water, it has been demonstrated that photosystem I of certain cyanobacteria can function in vivo independently in supporting virus production2, heterocyst functions3 and even photoheterotrophic growth4. We have demonstrated anoxygenic photosynthesis in a cyanobacterium Oscillatoria limnetica, also capable of oxygenic photosynthesis, which was isolated from the anaerobic H2S rich hypolimnion layer of the monomictic, hypersaline Solar Lake located on the desert margin of the Gulf of Elat, Israel5. During winter stratification, this layer is located below two plates of phototrophic sulphur bacteria (Chromatium violescens and Prosthecochloris sp.), and exhibits a dense cyanobacterial bloom with very high rates of primary production. We report here evidence for the photosystem I-driven CO2 photoassimilation in O. limnetica with H2S serving as sole electron donor through oxidation to elemental sulphur.

Photochemistry and PhotobiologyVolume 19, Issue 5 p. 379-382 EFFECT OF PHOTOOXIDATIVE CONDITIONS ON LEVELS OF SUPEROXIDE DISMUTASE IN ANACYSTIS NIDULANS Aaron Abeliovich, Aaron Abeliovich Department of Microbiological Chemistry, Hebrew University-Hadassah Medical School, Jerusalem, IsraelSearch for more papers by this authorDevora Kellenberg, Devora Kellenberg Department of Microbiological Chemistry, Hebrew University-Hadassah Medical School, Jerusalem, IsraelSearch for more papers by this authorMoshe Shilo, Moshe Shilo Department of Microbiological Chemistry, Hebrew University-Hadassah Medical School, Jerusalem, IsraelSearch for more papers by this author Aaron Abeliovich, Aaron Abeliovich Department of Microbiological Chemistry, Hebrew University-Hadassah Medical School, Jerusalem, IsraelSearch for more papers by this authorDevora Kellenberg, Devora Kellenberg Department of Microbiological Chemistry, Hebrew University-Hadassah Medical School, Jerusalem, IsraelSearch for more papers by this authorMoshe Shilo, Moshe Shilo Department of Microbiological Chemistry, Hebrew University-Hadassah Medical School, Jerusalem, IsraelSearch for more papers by this author First published: May 1974 https://doi.org/10.1111/j.1751-1097.1974.tb06526.xCitations: 57AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinkedInRedditWechat References Abeliovich, A. and M. Shilo (1972) J. Bacterial. 111, 682–689. Colowick, S. P. and N. O. Kaplan (Editors) (1955) Methods in Enzymology, Vol. 2, p. 482. Academic Press. New York . Gregory, E. M. and I. Fridovich (1973) J. Bcicteriol. 114, 543–548. Keele, B. B. Jr., J. M. McCord and I. Fridovich (1971) J. Biol. Chem. 246, 2875–2880. Lowry, O. H., N. H. Rosebrough, A. L. Farr and A. J. Randall (1951) J. Biol. Chem. 193, 265–275. McCord, J. M. and I. Fridovich (1969) J. Biol. Chem. 244, 6049–6055. McCord, J. M., B. B. Keele Jr. and I. Fridovich (1971) Proc. Natl. Acad. Sci. U.S. 68, 1024–1027. Citing Literature Volume19, Issue5May 1974Pages 379-382 ReferencesRelatedInformation