A laboratory based exposure of Microcystis and Oscillatoria cyanobacterial isolates to heterotrophic bacteria.

Biological control of cyanobacteria is a viable means of controlling nuisance bloom occurrences; however the majority of studies done are against Microcystis sp., with a commonly lytic effect caused. Filamentous cyanobacteria such as Oscillatoria are not as extensively studied in this area of biological control and are often part of Microcystis dominated blooms. This study employed heterotrophic bacterial isolates selected from bloom waters that indicated potential predatory behaviour against both filamentous and colonial cyanobacterial isolates. In comparison to a known Bacillus isolate, which is often reported among bacterial control agents, three other bacteria isolates were tested as control agents against non-axenic Oscillatoria and Microcystis cyanobacterial cultures. Assessments of cyanobacterial cell responses to the bacteria were conducted through water chemistry, chlorophyll a, alkaline phosphatase activity, microscopy and cyanotoxin measurements. The changes in these parameters were compared to untreated cyanobacterial cultures where no bacteria were added. The study found that at ratios of bacteria half that of Microcystis, minimal changes in chlorophyll a were observed, whilst Oscillatoria showed a decreased chlorophyll a more in the presence of isolates 1 and 3w. The assessment of alkaline phosphatase activity showed decreased activity in both cyanobacterial isolates exposed to the bacteria, relative to the untreated control sample. Microscopy analysis through fluorescence indicated that the attachment of the bacteria to the surface of the cyanobacteria hampered with the fluorescence and scanning electron microscopy indicated that the cells were damaged by the addition of the bacterial isolates. Cyanotoxin detection through the ELISA kit testing indicated that there was toxin reduction in samples treated with the bacterial isolates, with the highest reduction being close to 60% in the case of Microcystis sp. treated with isolate 3w. Similar reductions were noted in the filamentous cyanobacterium Oscillatoria, in the presence of isolate 1.

Biological floating bed and bio-contact oxidation processes for landscape water treatment: simultaneous removal of Microcystis aeruginosa, TOC, nitrogen and phosphorus.

The aim of this study was to identify algicidal bacteria J25 against the Microcystis aeruginosa (90.14%), Chlorella (78.75%), Scenedesmus (not inhibited), and Oscillatoria (90.12%). Meanwhile, we evaluate the SOD activity and efficiency of denitrification characteristics with Acinetobacter sp. J25. A novel hybrid bioreactor combined biological floating bed with bio-contact oxidation (BFBO) was designed for treating the landscape water, and the average removal efficiencies of nitrate-N, ammonia-N, nitrite-N, TN, TP, TOC, and algal cells were 91.14, 50, 87.86, 88.83, 33.07, 53.95, and 53.43%, respectively. A 454-pyrosequencing technology was employed to investigate the microbial communities of the BFBO reactor samples. The results showed that Acinetobacter sp. J25 was the dominant contributor for effective removal of N, algal cells, and TOC in the BFBO reactor. And the relative abundance of Acinetobacter showed increase trend with the delay of reaction time. Graphical abstract Biological floating bed and bio-contact oxidation (BFBO) as a novel hybrid bioreactor designed for simultaneous removal Microcystis aeruginosa, TOC, nitrogen, and phosphorus. And high-throughput sequencing data demonstrated that Acinetobacter sp. J25 was the dominate species in the reactor and played key roles in the removal of N, TOC, and M. aeruginosa. Proposed reaction mechanism of the BFBO.

Irreversibly increased nitrogen fixation in Trichodesmium experimentally adapted to elevated carbon dioxide.

Nitrogen fixation rates of the globally distributed, biogeochemically important marine cyanobacterium Trichodesmium increase under high carbon dioxide (CO2) levels in short-term studies due to physiological plasticity. However, its long-term adaptive responses to ongoing anthropogenic CO2 increases are unknown. Here we show that experimental evolution under extended selection at projected future elevated CO2 levels results in irreversible, large increases in nitrogen fixation and growth rates, even after being moved back to lower present day CO2 levels for hundreds of generations. This represents an unprecedented microbial evolutionary response, as reproductive fitness increases acquired in the selection environment are maintained after returning to the ancestral environment. Constitutive rate increases are accompanied by irreversible shifts in diel nitrogen fixation patterns, and increased activity of a potentially regulatory DNA methyltransferase enzyme. High CO2-selected cell lines also exhibit increased phosphorus-limited growth rates, suggesting a potential advantage for this keystone organism in a more nutrient-limited, acidified future ocean.

A preliminary study of the algicidal mechanism of bioactive metabolites of Brevibacillus laterosporus on Oscillatoria in prawn ponds.

The algae, Oscillatoria, is commonly found in prawn ponds and can lead to reduced productivity. We examined metabolites of the bacteria Brevibacillus laterosporus for algicidal qualities. To determine the possible algicidal mechanisms of these bioactive metabolites, different amounts of sterile filtrate of bacterial suspensions were added to cultures containing Oscillatoria. The dry weight, the concentrations of chlorophyll-a (chl-a), phycobiliprotein (PC, phycocyanin; APC, allophycocyanin; PE, phycoerythrin), and MDA (malondialdehyde) and the activities of SOD (superoxide dismutase), POD (peroxidase), and CAT (catalase) of algae were measured during the algicidal application. The results showed that lower concentrations of the sterile filtrate (addition ≤ 4 mL) accelerated the growth rate of Oscillatoria, but significant inhibition and lysis were observed with higher concentrations (addition ≥ 8 mL). In two trials (the additions were 8 mL and 10 mL, respectively), the algal dry weights were reduced by 26.02% and 45.30%, and the chl-a concentrations were decreased by 46.88% and 63.73%, respectively, after seven days. During the algicidal treatment, the concentrations of PC, APC, PE, and MDA and the activities of SOD, POD, and CAT were significantly increased in the early cultivation and declined quickly at later stages. Finally, the algae-lysing mechanism of the bioactive metabolites of the bacteria Brevibacillus laterosporus on Oscillatoria had been proposed.

Cylindrospermopsin accumulation and release by the benthic cyanobacterium Oscillatoria sp. PCC 6506 under different light conditions and growth phases.

We have studied the dynamics of cylindrospermopsin concentration (CYN) of a benthic cyanobacterium of the genus Oscillatoria under various light conditions over the different growth phases. The present study is the first one reporting on the effect of abiotic factors on the CYN accumulation and release by a benthic species. In particular we have measured the concentrations of both intracellular and extracellular CYN. We found that the total CYN content is highest during the exponential growth phase at intermediate light level (10 µE m(-2) s(-1)) and during the stationary growth phase at more extreme lower and higher light levels. Our results also indicate that the amount of the extracellular form varied between 56 % and 96 % of the total CYN concentrations. We found no relationship between CYN content and growth rates. These results suggest many similarities with planktonic species but also highlight some differences.

[Morphogenesis in a community of filamentous cyanobacteria].

Reversible differentiation was experimentally discovered in a community of modern filamentous cyanobacteria Oscillatoria terebriformis. Splitting of the initially uniform community into differentiated parts (strands, multiradiate aggregates, networks, etc.) occurs only for the duration of a function facilitating the activity of this community as an integral unit. The structures are formed as a result of regrouping of the filaments, without their specialization. A morphologically regulatory system (polygonal network) was found to develop under the impact of extreme factors. The levels of structural organization of filamentous cyanobacteria and multicellular eukaryotes were compared (individual cells in a filament--cell organelles; filaments--individual cells; community--organism), and the similarities and differences in morphogenesis of these groups were analyzed using the data on the embryonic regulation in multicellular eukaryotes. Spatial information in morphogenesis was shown to result not from direct realization of an inherited program but is created by the elements of integral organisms (cells and filaments) in the course of development.

Effects of shear and surface roughness on reducing the attachment of Oscillatoria sp. filaments on substrates.

The effects of surface roughness and shear on the attachment of Oscillatoria sp. algal filaments onto SS314 stainless steel coupons were investigated. Average surface roughness was used to systematically characterize the surface condition. An annular biofilm reactor with a spinning inner cylinder was used to create a uniform shear flow over the coupons. As far as the authors are able to establish, these systematic methods have yet to be used in the study of microalgae deposition. It was postulated that increasing average surface roughness would lead to an increase in the amount of algae deposited, whereas an increase in shear would lead to a decrease in algae deposition and reduce the algae lengths by way of fragmentation. The results indicate that an increasing surface roughness would increase the amount of algal strands that might deposit on the coupons, whereas shear was found to have the effect of reducing the amount of algae that might attach on the coupons.

Adaptation of cyanobacteria to the sulfide-rich microenvironment of black band disease of coral.

Black band disease (BBD) is a cyanobacteria-dominated microbial mat that migrates across living coral colonies lysing coral tissue and leaving behind exposed coral skeleton. The mat is sulfide-rich due to the presence of sulfate-reducing bacteria, integral members of the BBD microbial community, and the sulfide they produce is lethal to corals. The effect of sulfide, normally toxic to cyanobacteria, on the photosynthetic capabilities of five BBD cyanobacterial isolates of the genera Geitlerinema (3), Leptolyngbya (1), and Oscillatoria (1) and six non-BBD cyanobacteria of the genera Leptolyngbya (3), Pseudanabaena (2), and Phormidium (1) was examined. Photosynthetic experiments were performed by measuring the photoincorporation of [(14)C] NaHCO(3) under the following conditions: (1) aerobic (no sulfide), (2) anaerobic with 0.5 mM sulfide, and (3) anaerobic with 0.5 mM sulfide and 10 microM 3-(3',4'-dichlorophenyl)-1,1-dimethylurea (DCMU). All five BBD cyanobacterial isolates tolerated sulfide by conducting sulfide-resistant oxygenic photosynthesis. Five of the non-BBD cyanobacterial isolates did not tolerate sulfide, although one Pseudanabaena isolate continued to photosynthesize in the presence of sulfide at a considerably reduced rate. None of the isolates conducted anoxygenic photosynthesis with sulfide as an electron donor. This is the first report on the physiology of a culture of Oscillatoria sp. found globally in BBD.

[A laboratory model of the cyanobacterial mat from the Kotel'nikovskii hot spring (Baikal Region)].

A laboratory model of the cyanobacterial community of the Kotel'nikovskii hot spring (Baikal Region) was developed. A step-by-step description of the algocenosis formation along both the time and temperature gradient was given. The natural and laboratory mats were compared, and the major differences in the qualitative and quantitative composition of the cyanobacterial community were revealed. The laboratory algocenosis was stratified by species composition and was characterized by rapid replacement of the dominant cyanobacterial species depending on the temperature gradient. The formation of the community structure occurred over the 18 days of the experiment. In space and time, the sequence of species emergence in the cyanobacterial mat was as follows: Mastigocladus laminosus --> Phormidium tenue --> Ph. ambiguum --> Ph. valderiae. The species composition of the laboratory mat was similar to that of the natural mat; however it was found to be less diverse.