Algal Extracellular Products Research Articles

Community level physiological study of algicidal bacteria in the phycospheres of Skeletonema costatum and Scrippsiella trochoidea

Bacteria in the phycosphere have a unique ecological relationship with host algae due to their utilization of algal extracellular products as nutrients. Some bacteria control the growth of algal cells and even lyse them. The diversity of bacteria and their community dynamics in the phycosphere of microalgae are still relatively little understood, especially of those associated with red tide-causing algae. In this study, scanning electron microscope (SEM) images of algal cell morphology revealed that the phycosphere bacteria of the red tide-causing algae, Skeletonema costatum and Scrippsiella trochoidea, could lyse them within 72h. The community level physiology of the algicidal bacteria was studied using Biolog ECO microplates, a common method for the ecological study of microbial communities. The average well color development (AWCD) values of bacteria in the phycospheres of both species were low, indicating that the bacteria had low metabolic activity overall. The diversity indices were both lower than the bacterial diversity from natural environments. However, the bacteria associated with S. trochoidea demonstrated a higher AWCD value and diversity than those in the phycosphere of S. costatum. The utilization of carbon sources significantly changed at different lytic times, reflecting that the bacterial community structure changed during the algae-lysing process. These results revealed that the bacterial communities in phycospheres had a simple structure and low diversity. When the balance between algae and bacteria broke down, the total bacterial density increased while the algicidal bacteria accumulated and became the dominant species, changing the bacterial community structure in this micro-ecosystem.

Factors controlling induction of reproduction in algae—review: the text

This review surveys on the influence of different environmental factors like light (intensity, quality, photoperiod), temperature, season, nutrients (inorganic, organic), biotic factors (algal extracellular products, bacterial association, animals grazing), osmotic stress, pH of the medium, wave motion and mechanical shock, pollution, and radiations (UV, X-rays, gamma radiation) on the induction (or inhibition) of algal reproduction like cell division in unicellular algae, and formation of zoospores, aplanospores, akinetes, cysts, antheridia, oogonia, zygospores, etc.

Ozonation By-products and Determination of Extracellular Release in Freshwater Algae and Cyanobacteria

This work identifies the cyanobacterial and algal extracellular products (ECPs) and their derived byproducts during preozonation. Laboratory experiments were performed on two cyanobacterial species (Oscillatoria tenuisa and Microcystis aeruginosa) and one algal species (Chlorella sp.) dominating eutrophic reservoirs. Gas chromatography, coupled with high-resolution electron-impact mass spectrometry (GC/EI-MS), and high-performance anion-exchange chromatography (HPAEC) was adopted. Over 20 compounds were detected in the mass spectra analyses of the cyanobacterial and algal extracts (including cells and filtrates). The main identified ECPs were classified as monosaccharides, fatty acids, hydrocarbons, and aldehydes. Odor-causing substances were also present in the cyanobacteria, such as trans-1,10-dimethyl-trans-9-decalol (geosmin) and 2-methylisoborneol (2-MIB). The results from ozonated cyanobacteria and algae indicated that the dissolved organic carbon (DOC) content of culture suspensions increased during ozonation. Most of the additional DOC is produced by the increased liberation of ECPs to the bulk phase. Several byproducts were present in the ozonated cyanobacterial and algal cultures: a total of 22 different organic compounds were detected—mostly aldehydes and phthalates.

Evaluation of extracellular products and mutagenicity in cyanobacteria cultures separated from a eutrophic reservoir

The algal extracellular products (ECPs) in three cultures of cyanobacteria species (Anabaena, Microcystis, and Oscillatoria) dominating the eutrophic reservoir populations and their toxins have been investigated in the present work. Using gas chromatography coupled with high-resolution electron-impact mass spectrometry (GC/EI-MS) and high performance anion-exchange chromatography (HPAEC) techniques, more than 20 compounds were found in the algal culture (including cells and filtrates) extracts. The main identified ECPs were classified to polysaccharides, hydrocarbons, and aldehydes. Odor causing substances such as trans-1,10-dimethyl-trans-9-decalol (geosmin) and 2-methylisoborneol (2-MIB)were also found in the algal cultures. The potential mutagenicity of the algal suspensions was also studied with the Ames test. The organic extracts of the algal suspension from the axenic cultures were mutagenicity in TA98 without S9 mix and in TA100 with and without S9 mix. The results indicate that the ECPs of three algae species dominating the eutrophic reservoir were mutagenic clearly in the bacterial test.

Role of Bipolar Pulsed DBD on the Growth of Microcystis aeruginosa in Three-Phase Discharge Plasma Reactor

Algae in drinking water supplies often bring about impact on the water treatment. In this study, a bipolar pulsed dielectric barrier discharge system in three-phase discharge plasma reactor was constructed for investigating its ability to control excessive growth of cyanobacteria, Microcystis aeruginosa. Experimental results show there was almost no change in optical density immediately after the interruption of electrical discharge, but the decreasing trend of optical density, cell density and chlorophyll-a content was obvious during the incubation period, indicating a significant residual effect of electrical discharge process on the algal growth inhibition. Scanning electron microscopy investigation of algae revealed surface damage, apparent leakage of intracellular contents and pores formed after electrical discharge process, which showed that algal cells had no potential to survive and grow. Compared with the control sample, it was observed that electrical discharge on the algal extracellular products has almost no residual effect and the growth rate of algae slightly decreased before three days storage. Hydrogen peroxide was produced by electrical discharge in the μM level and showed a first-order decay. But at such level, the external addition of hydrogen peroxide alone is not likely to cause the residual effect. These results implicated that the growth inhibition of M. aeruginosa was mainly caused by electrical discharge process, and it made the algal cells lose ability to survive, demonstrating the considerable potential of such an alternative process for efficient water purification.

Direct and indirect inactivation of microcystis aeruginosa by UV-radiation

Excessive algal growth in drinking water sources like lakes and reservoirs is responsible for filter-clogging, undesirable taste and odor, disinfection-by-product formation and toxin generation. Although various methods are currently being used to control algal bloom, their successes are limited. Some water utilities routinely use copper sulfate to control excessive algal growth. But there is a growing concern against its use mainly because it is non-specific to target algae and kills many non-target species. In this study, the scope of using UV-radiation to control algal growth was assessed using Microcystis aeruginosa as test species. A UV-dose of 75 mW s cm −2 was found to be lethal to M. aeruginosa. A smaller dose of 37 mW s cm −2 prevented growth for about 7 days. It was found that UV-radiation may increase the specific gravity of the cells and thus may adversely affect the ability of the cells to remain in suspension. Three days after a UV-dose of 75 mW s cm −2, almost all the cells settled to the bottom of the incubation tubes, whereas all the unirradiated cells remained in suspension. It was also observed that UV-radiation on algal extracellular products has a significant residual effect and can contribute to algal growth control. The extent of residual effect depends on the UV-dose and can continue even for 7 days. UV-radiation was found to produce H 2O 2 in the μM level concentration. But at such level, H 2O 2 itself is not likely to cause the residual effect that was found in this study.

Green algal extracellular products regulate antialgal toxin production in a cyanobacterium.

Many bacterial genes and virulence factors are regulated by interbacterial and/or host-parasite chemical signals. We demonstrate that toxin production by a free-living freshwater cyanobacterium is regulated in part by the presence of extracellular products of a eukaryotic green alga. In growth experiments, extracellular products made by the cyanobacterium Anabaena flos-aquae contained both anatoxin and microcystin, and significantly reduced the yield of Chlamydomonas reinhardtii, a green alga. Based on experiments in which we added purified toxins to C. reinhardtii cultures, we believe that microcystin was responsible for the growth reduction. A. flos-aquae produced anatoxin constitutively when grown alone, but anatoxin concentration increased in the presence of C. reinhardtii elicitors. Microcystin accumulation depended on the growth phase; however, high concentrations of C. reinhardtii extracellular products completely inhibited microcystin accumulation. Our results demonstrate that cyanobacterial toxin production may be regulated by complex growth phase-dependent and environmental chemical cues, and suggest that secreted chemicals can mediate the outcome of competition between the cyanobacterium A. flos-aquae and the green alga C. reinhardtii.

The removal of algal biomass and extracellular products from water

Abstract The removal of algal biomass and algal extracellular products (ECPs) from eutrophic water is studied using various physical chemical methods including coagulation/precipitation, powdered activated carbon (PAC) adsorption and combination of coagulation/ precipitation and activated carbon adsorption. The removal efficiencies of algae and TOC are 96% and 81%, respectively, by coagulation/ precipitation method. Moreover, dissolved organic carbon (DOC) is divided into four groups based on molecular weight distribution. It is found that coagulation/ precipitation process has good DOC removal efficiency for high molecular weight groups whereas PAC adsorption is particularly effective of the removal of DOC of low molecular weight. It is also discovered that the removal efficiency is synergistic by coagulation/ precipitation followed by PAC adsorption. The formations of THMFP/ DOC and AOXFP/DOC are higher with high molecular weight groups than those with low molecular weight groups.

Planktonic bacterial DNA and RNA synthesis from algal extracellular products in a eutrophic lake

In order to better understand bacterial growth in the natural environment, a tracer experiment was carried out by adding [14C]bicarbonate to samples from a eutrophic lake and enclosures which were constructed inside the lake to provide different substrate conditions. It was shown that extracellular dissolved organic carbon (EDOC) released from photosynthetic phytoplankton was one of the most important carbon sources for the growth of planktonic bacteria in the aquatic environment studied here. About 5% of photosynthetically fixed 14C was transferred to the bacterial fraction between 4 and 8 h after the addtion of the [14C]bicarbonate. This increased to 10% during the following 16 h in the dark. Between 50% and 60% of bacterial 14C from EDOC was transformed to bacterial macromolecules. Analysis of cellular components showed that 36–39% of macromolecules produced were DNA during the light incubation, although the proportion of DNA relative to total macromolecules decreased in the dark. RNA synthesis increased with time, from 25% to 38% during the dark incubation. There was a correlation between bacterial growth rates and the ratio of RNA/DNA synthesized from EDOC (r = 0.81). However, the RNA/DNA ratio was very small, 1.8 for all samples examined, compared with previous data obtained for the laboratory bacteria. This is probably due to the very slow growth rate of the natural planktonic bacteria.

Planktonic bacterial DNA and RNA synthesis from algal extracellular products in a eutrophic lake

In order to better understand bacterial growth in the natural environment, a tracer experiment was carried out by adding [14C]bicarbonate to samples from a eutrophic lake and enclosures which were constructed inside the lake to provide different substrate conditions. It was shown that extracellular dissolved organic carbon (EDOC) released from photosynthetic phytoplankton was one of the most important carbon sources for the growth of planktonic bacteria in the aquatic environment studied here. About 5% of photosynthetically fixed 14C was transferred to the bacterial fraction between 4 and 8 h after the addtion of the [14C]bicarbonate. This increased to 10% during the following 16 h in the dark. Between 50% and 60% of bacterial 14C from EDOC was transformed to bacterial macromolecules. Analysis of cellular components showed that 36–39% of macromolecules produced were DNA during the light incubation, although the proportion of DNA relative to total macromolecules decreased in the dark. RNA synthesis increased with time, from 25% to 38% during the dark incubation. There was a correlation between bacterial growth rates and the ratio of RNA/DNA synthesized from EDOC (r = 0.81). However, the RNA/DNA ratio was very small, 1.8 for all samples examined, compared with previous data obtained for the laboratory bacteria. This is probably due to the very slow growth rate of the natural planktonic bacteria.

Bacterial utilization of algal extracellular products in a southwestern reservoir

Rates of carbon flow from phytoplankton to bacteria were estimated for Lake Arlington, Texas. The lake is a warm (annual temperature range 7 to 35 °C), shallow, monomictic reservoir with limited macrophyte development in the littoral zone. Samples were collected from 6 depths within the photic zone from a site located over the deepest portion of the lake. Primary production and exudate production were calculated from NaH14CO3 incorporation. Bacterial production was calculated from [methyl-3H]-thymidine incorporation. Depth averaged primary production ranged from a seasonal low of 9.0 µg C l−1 h−1 in January to a seasonal maximum of 153 µg C l−1 h−1 during holomixis in September. Annual depth-averaged production was 67.8 ± 7.3 µg C l−1 h−1. Exudate production ranged between 21.9 and 54.2% of primary production and annually averaged 30.8%. Bacterial production ranged between 1.7 and 46.0 µg C l−1 h−1 and annually averaged 16.0 ± 1.9 µg C l−1 h−1. Bacteria processed approximately 70% of exudate and incorporated 35% into biomass. Bacterial production was positively correlated with total primary production (r = 0.38, p < 0.003, n = 6), particulate primary production (r = 0.34, p < 0.004, n = 70) and bacterial uptake of exudate (r = 0.43, p < 0.001, n = 68). While exudate was readily utilized by bacteria it dit not appear to be produced in sufficient quantity or at a sufficient rate to serve as the sole or a major source of carbon supporting bacterial growth.

Characterization of Native Bacteria and Their Utilization of Algal Extracellular Products by a Mixed-Substrate Kinetic Model

Assimilation and mineralization og 14C labelled extracellular products (EOC) by native bacterial populations were followed in a diel study and from early spring through autumn in two eutrophic Danish lakes. Kinetic analyses according to a mixed-substrate kinetic model always revealed linear kinetics. The method was found useful in unveiling in situ specific algal-bacterial associations mediated through the release of EOC from the primary producers. Further, bacterial adaptation toward the phycosphere of Microcystis aeruginosa could be detected by following the shift in X-intercepts for the lines of net uptake and respiration during the development of a bloom of M. aeruginosa. By simultaneous measurements of particulate primary production, EOC release and transport of EOC to the bacteria by a differential filtration technique, it is shown that the method presented does not generally estimate changes in the kinetic parameters, but does reveal qualitative changes. It is concluded that the mixed-substrate method is a powerful approach for elucidating specific algal-bacterial associations in situ, even in highly complex eutrophic environments.

Assessing Phytoplankton and Bacterioplankton Production During Early Spring in Lake Erken, Sweden

The spring development of both phytoplankton and bacterioplankton was investigated between 18 April and 7 May 1983 in mesotrophic Lake Erken, Sweden. By using the lake as a batch culture, our aim was to estimate, via different methods, the production of phytoplankton and bacterioplankton in the lake and to compare these production estimates with the actual increase in phytoplankton and bacterioplankton biomass. The average water temperature was 3.5 degrees C. Of the phytoplankton biomass, >90% was the diatom Stephanodiscus hantzchii var. pusillus, by the peak of the bloom. The C and O(2) methods of estimating primary production gave equivalent results (r = 0.999) with a photosynthetic quotient of 1.63. The theoretical photosynthetic quotient predicted from the C/NO(3) N assimilation ratio was 1.57. The total integrated incorporation of [C]bicarbonate into particulate material (>1 mum) was similar to the increase in phytoplankton carbon determined from cell counts. Bacterioplankton increased from 0.5 x 10 to 1.52 x 10 cells liter ( approximately 0.5 mug of C liter day). Estimates of bacterioplankton production from rates of [H]thymidine incorporation were ca. 1.2 to 1.7 mug of C liter day. Bacterial respiration, measured by a high-precision Winkler technique, was estimated as 4.8 mug of C liter day, indicating a bacterial growth yield of 25%. The bulk of the bacterioplankton production was accounted for by algal extracellular products. Gross bacterioplankton production (production plus respiration) was 20% of gross primary production, per square meter of surface area. We found no indication that bacterioplankton production was underestimated by the [H]thymidine incorporation method.

Organohalide formation on chlorination of algal extracellular products

Organohalide formation on chlorination of algal extracellular products

Bacterial adaptation to low-nutrient conditions as studied with algal extracellular products

Kinetic analyses indicate that members of natural bacterial populations from 2 marine environments near Woods Hole, MA, possess enzyme-mediated transport systems which permit utilization of(14)C-labeled extracellular organic C ((14)C-EOC) prepared from the algae,Skeletonema costatum, Thalassiosira pseudonana, andDunaliella tertiolecta, and supplied over a concentration range of 15-150μC·liter(-1). It is shown that previous exposure of the bacteria to the EOC from these algae cannot explain the linear kinetic patterns obtained. Therefore, the ability to utilize algal EOC at low concentrations is a general feature of metabolically active bacterial populations. Further, as the native bacteria do not restrict this ability to a specific EOC pool, the results are consistent with the hypothesis that bacteria adapted to low nutrient environments possess uptake systems of high substrate affinity and low substrate specificity. Elevation of substrate levels with as little as 10 mg·1(-1) peptone is shown to favor development of a bacterial population that lacks these adaptations. Standard enrichment techniques typically result in the isolation of bacteria that are poor models for evaluating the ecology of native microbiota.

The isolation and growth of axenic cultures of planktonic blue—green algae

A procedure for isolating axenic cultures of planktonic blue-green algae is described that relies on a filtration procedure to produce a high filament: bacteria ratio and a subsequent serial dilution to isolate axenic algal filaments. Six axenic cultures have been prepared and their growth kinetics compared with the corresponding bactericized cultures. In continuous light, two axenic cultures exhibited sub-optimal growth whereas the remainder grew essentially as well as their bactericized counterparts. By contrast, under a light: dark regime two axenic cultures exhibited significantly better growth, and another, significantly poorer growth than the bactericized cultures. The causal factors of the poor growth of Oscillatoria agardhii Gom. were investigated, and it was concluded that the role of bacteria may be an active metabolic one, possibly involving the recycling of algal extracellular products.

Bacterial utilization of algal extracellular products. 3. The specificity of algal‐bacterial interaction

Kinetic analyses were made of the utilization of 14C‐labeled algal extracellular products (EP) by bacterial populations in continuous algal cultures containing steady state Skeletonema costatum or Dunaliella tertiolecta. The development of bacteria adapted to the respective algal species was revealed by gradual evolution of a common X‐intercept for net EP uptake and respiration lines from initially disparate estimates. When the adapted populations were given labeled EP prepared from other algal species, linear kinetics were retained but the X‐intercepts for net uptake and respiration failed to coincide. Bacterial response to a given algal EP pool does not necessarily preclude enzyme‐mediated utilization of organic substrates from other species. Rapid utilization of algal EP appears to be a consequence of bacterial adaptation to existence under dilute nutrient conditions rather than a response to a specific alga. Prolonged exposure to a single alga may favor the development of bacterial populations in which metabolism is limited by enzyme‐mediated transport of the compounds available in its EP pool, but this phenomenon is less significant ecologically than the general stimulation of bacterial activity effected by the increased supply of these compounds.

Bacterial uptake of algal extracellular products: an experimental approach

Methods for partitioning planktonic algal and bacterial populations were examined. If samples were filtered under gravity through a 1 μm pore size Nuclepore polycarbonate membrane the algae were retained on the filter and most (usually &gt; 80%) of the bacteria were found in the filtrate. The application of any vacuum or pressure during this process resulted in the appearance of chlorophyll in the filtrate. In radiotracer experiments this would lead to an overestimate of 14C incorporation into the bacteria. There was excellent agreement between measurements of partition efficiency by epifluorescence direct counts of bacteria and by uptake of trace quantities of tritiated glucose. The methods were applied to the measurement of algal excretion of dissolved organic matter and its uptake by bacteria over light‐dark cycles. An illuminated water bath was adapted to provide shortened (3–24 h) light‐dark cycles which could be used to examine interactions between individual algal and bacterial species. Estimates of bacterial heterotrophic production based on the assimilation of labelled algal extracellular products were lower than those calculated from the incorporation of SO2‐4.

Diel changes in numbers and activities of bacterioplankton in a reservoir in relation to algal production

The changes in bacterial numbers, relative growth rates, and glucose uptake kinetics were studied in the surface layer of a reservoir during several 24‐h observation periods at intervals of 3 or 6 h, and once a day at intervals of 4 or 6 weeks from April through October. Microscopic and plate counts did not show any diel periodicity. All the other measures had regular diel patterns and the range of diel variation increased with increasing algal production. The diurnal average relative growth rates, Kt + Sn values, and turnover times were distinctly higher than the nocturnal ones and there were also characteristic diel changes in glucose uptake kinetics during the periods of algal activity. The diel changes in bacterial net uptake rate of algal extracellular products in autumn samples were twice as high as the maximum glucose uptake rate. Only for microscopic counts and maximum glucose net uptake rates were the diel variations significantly lower than the seasonal variation. For other parameters, the diel and seasonal variations were similar.

Bacterial Uptake of Photosynthetic Carbon from Freshwater Phytoplankton

Microheterotrophic uptake of algal extracellular products was studied in two eutrophic lakes in southern Sweden. Size fractionation was used in H14CO3 uptake experiments to measure l4C fixation in total particulate, small particulate and dissolved organic fractions. Carbon fixed in algal photosynthesis was recovered as dissolved and small particulate 14C, representing excretion and bacterial uptake of algal products. Estimated gross extracellular release was low in these eutrophic systems, 1 to 7% of total 14C uptake per m2 lake surface. From 28 to 80% of 14C released was recovered in the small particulate fraction after ca. 4 h incubation. This percentage was uniform within each depth profile, but varied directly with in situ water temperature. Laboratory time-series incubations indicated steady state for the pool of algal extracellular products on one occasion, while increasing pool size was indicated in the remaining two experiments. Uptake of photosynthetic carbon to small particles in situ was 32 to 95% of estimated heterotrophic bacterial production (as dark '4C02 uptake) on four occasions. While excretion apparently was not an important loss of carbon for phytoplankton, it may have represented an important carbon source for planktonic bacteria.