Production Of Extracellular Carbohydrates Research Articles

Inhibitory effect of modified atmosphere packaging on Escherichia coli O157:H7 in fresh-cut cucumbers (Cucumis sativus L.) and effectively maintain quality during storage

Modified atmosphere packaging (MAP) can inhibit microbial growth and prolong shelf life of fresh-cut cucumbers. This study compared the effects of different packaging gases on the growth of E. coli O157:H7 and sensory characteristics of fresh-cut cucumbers. Changes in key movement, adhesion, and oxidative stress genes expression of strain under optimal MAP and air were determined. Cell population density, the extracellular carbohydrate complex content and expression of curli fimbriae were evaluated. Results revealed that the growth of E. coli O157:H7 in fresh-cut cucumbers could be effectively inhibited under MAP (atmosphere = 2% O2, 7% CO2, 91% N2), and better maintained the sensory characteristics. Furthermore, the inhibition mechanism was revealed by inhibiting the expression of movement (fliC), adhesion (eaeA) and oxidative stress (rpoS and sodB) genes in E. coli O157:H7, reducing biofilm formation, extracellular carbohydrate production and curli fimbriae expression. Proper MAP can maintain the quality and safety of fresh-cut cucumbers.

Effect of removal of bacteria on the biomass and extracellular carbohydrate productivity of Botryococcus braunii

Botryococcus braunii CCALA778 is a green microalga that can produce large amounts of extracellular carbohydrates and therefore is a potential host for industrial applications such as materials, food and pharmaceutical products. The downside of B. braunii is its slow growth and therefore, improvements on the biomass productivity or carbohydrate production will make this microalga more attractive for industrial exploitation. Microalgae grow naturally in the presence of bacteria and these can be beneficial or antagonistic. In outdoor cultivation systems, contamination by bacteria is common. The role or effects of bacteria present in B. braunii CCALA778 are not yet fully elucidated. We used UV-C treatment to reduce bacterial abundance in B. braunii CCALA778 cultures and 16S rRNA gene amplicon MiSeq sequencing for bacterial community analysis. The effect of the reduced amount of bacteria on biomass growth and production of extracellular carbohydrates was analysed. It is shown that UV-C treatment can reduce the bacterial population substantially without harming B. braunii. Bacteria removed by UV-C were antagonistic to B. braunii CCALA778 as in their absence production of biomass and extracellular carbohydrates was enhanced significantly. CCALA778 treated with UV-C accumulated 826 ± 61 mg L−1 of extracellular carbohydrates by day 15 compared with 422 ± 135 mg L−1 accumulated extracellular carbohydrates in the untreated culture.

Harvesting carbohydrate-rich Arthrospira platensis by spontaneous settling

The filamentous cyanobacterium Arthrospira platensis is an attractive feedstock for carbohydrate-based biofuels because it accumulated up to 74% of carbohydrates when nitrogen stressed. Nitrogen stressed A. platensis also settled spontaneously, and this occurred simultaneously with carbohydrates accumulation, suggesting a link between both phenomena. The increased settling velocity was neither due to production of extracellular carbohydrates, nor due to degradation of gas vacuoles, but was caused by an increase in the specific density of the filaments as a result of accumulation of carbohydrates under the form of glycogen. Settling velocities of carbohydrate-rich A. platensis reached 0.64mh−1, which allowed the biomass to be harvested using a lamella separator. The biomass could be concentrated at least 15 times, allowing removal of 94% of the water using gravity settling, thus offering a potential application as a low-cost and high-throughput method for primary dewatering of carbohydrate-rich A. platensis.

CARBOHYDRATE RELEASE BY A SUBTROPICAL STRAIN OF SPONDYLOSIUM PYGMAEUM (ZYGNEMATOPHYCEAE): INFLUENCE OF NITRATE AVAILABILITY AND CULTURE AGING1

This paper describes the influence of nitrate availability on growth and release of dissolved free and combined carbohydrates (DFCHOs and DCCHOs) produced by Spondylosium pygmaeum (Cooke) W. West (Zygnematophyceae). This strain was isolated from a subtropical shallow pond, located at the extreme south of Brazil (Rio Grande, RS). Experiments were carried out in batch culture, comparing two initial nitrate levels (10/100 μM) in the medium. Growth was monitored by direct microscopic cell counts and chl a content. Nitrate consumption was determined by ion chromatography, while the production of extracellular carbohydrates was monitored by the phenol‐sulfuric method. The monosaccharide compositions of DFCHOs and DCCHOs were determined in each growth phase by HPLC with pulse amperometric detection (HPLC‐PAD). At the end of the experiment, the total composition of extracellular polysaccharide (EPS) molecules >12 kDa was determined by gas chromatography. Nitrate availability had no influence on S. pygmaeum cell density at any phase. On the other hand, chl a content decreased after a few days growth when the availability of nitrate was restricted, but continued to rise when nitrate was plentiful. Also, nitrate depletion was faster at 10 μM nitrate. No influence of the growth phase or nitrate availability on the total carbohydrates (TDCHOs) released per cell was observed. Only DCCHOs were released by S. pygmaeum, and the composition varied between growth phases, especially at lower nitrate availability. EPS molecules >12 kDa were composed mainly of xylose, fucose, and galactose, as for other desmids. However, a high N‐acetyl‐glucosamine content was found, uniquely among desmid EPSs.

Responses of estuarine intertidal microphytobenthic algal assemblages to enhanced ultraviolet B radiation

AbstractAs a result of ozone depletion, ground doses of ultraviolet B (UVB) radiation in the mid latitudes of the Northern Hemisphere have increased since the 1980s, and current predictions indicate no possible alleviation until at least post 2020. Mudflats and sandflats are important coastal‐zone habitats, and support extensive biofilms of benthic microalgae (microphytobenthos). In intertidal situations, these assemblages are exposed to high levels of UVB radiation during periods of tidal exposure. Exposure of intertidal biofilms dominated by epipelic (mud‐inhabiting) diatoms to 0, 0.18 or 0.35 W m−2 UVB radiation for between 4 and 10 days resulted in no significant decreases in the maximum PSII quantum efficiency (Fv/Fm) throughout diel exposure periods. Although the quantum efficiency of electron transport (Fq′/Fm′) showed significant reductions early in some experiments, the major response was an increase in Fq′/Fm′ in UVB exposed biofilms. This increase in Fq′/Fm′ was suggestive of a protective vertical migration down into the sediment. Single‐cell and whole biofilm fluorescence imaging demonstrated, for the first time, that motile diatoms are able to detect UVB radiation independently of UVA or photosynthetically active radiation (PAR) and migrate rapidly down (within 15 min) into the sediments to avoid it. This behavioural acclimation mechanism appears to prevent significant accumulation of UVB induced damage to the algae. UVB exposure had no significant effect of biofilm photosynthesis (measured by 14C carbon fixation), but did alter organic carbon allocation patterns, with significantly less new carbon allocated to intracellular storage (glucan) and extracellular colloidal carbohydrate fractions. Significant reductions in the sediment standing stocks of chlorophyll a (Chl a), colloidal carbohydrates, extracellular polymeric substances (EPS) were seen after 7 days of UVB exposure. This study showed that marine intertidal benthic diatoms use a behavioural strategy to avoid exposure to UVB and that this response is effective as a short‐term protection mechanism against UVB damage. However, altered carbon allocation patterns feed forward over time into changes in biofilm biomass and sediment carbohydrate dynamics. This suggests that continual long‐term exposure to UVB may impact on sediment carbon cycling and trophic interactions and on the stabilization of sediments by microalgal biofilms through their production of extracellular carbohydrates.

Bacteria–algae association in batch cultures of phytoplankton from a tropical reservoir: the significance of algal carbohydrates

Summary 1. The dissolved organic matter, especially carbohydrates, released by phytoplanktonic organisms may be ecologically important, through its influence on carbon cycling and microbial diversity. Here axenic cultures of three phytoplanktonic species, Cryptomonas tetrapyrenoidosa (Cryptophyceae), Staurastrum orbiculare (Zygnematophyceae) and Thalassiosira duostra (Bacillariophyceae), were inoculated with a microbial community from the same habitat in which the algae had been isolated (a tropical reservoir). Replicate cultures were not inoculated.2. In both axenic and co‐inoculated cultures, phytoplanktonic density and extracellular carbohydrate production were monitored microscopically and by high performance liquid chromatography with a pulse amperometric detector, respectively. Bacterial population density was also monitored by epifluorescence microscope in the microbial co‐inoculated cultures.3. Both bacterial and phytoplanktonic densities increased for 11 days in all cases. The use of extracellular carbohydrates by bacteria was also showed for all phytoplanktonic species. Of the three species of phytoplankton, only T. duostra had a faster population growth in the presence of bacteria, and reached a higher biomass than in axenic culture.

Effects of Salt Stress on Carbohydrate Metabolism in Desert Soil Alga Microcoleus vaginatus Gom.

AbstractThe effects of salt stress on carbohydrate metabolism in Microcoleus vaginatus Gom., a cyanobacterium isolated from desert algal crusts, were investigated in the present study. Extracellular total carbohydrates and exopolysaccharides (EPS) in the culture medium produced by M. vaginatus increased significantly during the growth phase and reached a maximum during the stationary phase. The production of extracellular carbohydrates also significantly increased under higher salt concentrations, which was attributed to an increase in low molecular weight carbohydrates. In the presence of NaCl, the production of cellular total carbohydrates decreased and photosynthetic activity was impaired, whereas cellular reducing sugars, water‐soluble sugars and sucrose content and sucrose phosphate synthase activity increased, reaching a maximum in the presence of 200 mmol/L NaCl. These parameters were restored to original levels when the algae were transferred to a non‐saline medium. Sodium and K+ concentrations of stressed cells decreased significantly and H+‐ATPase activity increased after the addition of exogenous sucrose or EPS. The results suggest that EPS and sucrose are synthesized to maintain the cellular osmotic equilibrium between the intra‐ and extracellular environment, thus protecting algal cells from osmotic damage, which was attributed to the selective exclusion of cellular Na+ and K+ by H+‐ATPase.(Managing editor: Ping He)

Characterization of Bordetella pertussis growing as biofilm by chemical analysis and FT-IR spectroscopy

Although Bordetella pertussis, the etiologic agent of whooping cough, adheres and grows on the ciliated epithelium of the respiratory tract, it has been extensively studied only in liquid cultures. In this work, the phenotypic expression of B. pertussis in biofilm growth is described as a first approximation of events that may occur in the colonization of the host. The biofilm developed on polypropylene beads was monitored by chemical methods and Fourier transform infrared (FT-IR) spectroscopy. Analysis of cell envelopes revealed minimal differences in outer membrane protein (OMP) pattern and no variation of lipopolysaccharide (LPS) expression in biofilm compared with planktonically grown cells. Sessile cells exhibited a 2.4- to 3.0-fold higher carbohydrate/protein ratio compared with different types of planktonic cells. A 1.8-fold increased polysaccharide content with significantly increased hydrophilic characteristics was observed. FT-IR spectra of the biofilm cells showed higher intensity in the absorption bands assigned to polysaccharides (1,200-900 cm(-1) region) and vibrational modes of carboxylate groups (1,627, 1,405, and 1,373 cm(-1)) compared with the spectra of planktonic cells. In the biofilm matrix, uronic-acid-containing polysaccharides, proteins, and LPS were detected. The production of extracellular carbohydrates during biofilm growth was not associated with changes in the specific growth rate, growth phase, or oxygen limitation. It could represent an additional virulence factor that may help B. pertussis to evade host defenses.

Chemical and biochemical parameters of cultured diatoms and bacteria from the Adriatic Sea as possible biomarkers of mucilage production

Bacteria and diatom strains from the Adriatic Sea were investigated, under standard and altered environmental conditions, for carbohydrate production and for the presence of specific biomarkers. Algae from P-depleted cultures showed an increase in extracellular carbohydrate production, a significantly lower chlorophyll a content and unchanged total lipid levels. However, the fatty acid composition of algal cultures was severely affected by low P levels, in that, total saturated and monounsaturated fatty acids increased and total polyunsaturated fatty acids decreased. Marine heterotrophic bacteria resulted enriched by 4 to 6 orders of magnitude in mucilage samples respect to surrounding seawater, unlike other groups of bacteria such as the non-halophylic heterotrophs. The major fatty acids detected in bacteria were 16 : 0 and 18 : 1 n − 7; the uneven fatty acids 17 : 0i, 17 : 0 and 17 : 1 also constituted an important component of various strains and, as a result, the total monounsaturated fraction represented the main component of total fatty acids. All the mucilage samples analysed shared the same general fatty acid composition features with a high amount of saturated components, especially 16 : 0; typical marine polyunsaturated fatty acids, such as 20 : 5 n − 3 and 22 : 6 n − 3, were found at very low levels. With regard to the sterol composition, the analysed algal species and bacteria showed that different compounds prevailed in the different species, and under P-deprivation sterol distribution resulted differently affected in the various algal species. In mucilage samples an overall prevalence of cholesterol was observed and, among 4α-methylsterols, constantly present, dinosterol prevailed in all samples. Vibrational IR spectroscopic analyses confirmed the main results obtained with the GC analysis: a higher unsaturation degree in nutrient replete diatom cultures than in P-depleted ones, a lower amount of P-containing compounds in the latter, bacterial lipid profiles with a high amount of free carboxylic acids and/or ketones and a low unsaturation degree and, finally, mucilage samples with a very low unsaturation degree. All these results allowed some speculations on the involvement of the various microbial and phytoplankton components in mucilage genesis.

Partial characterisation of exopolysaccharides exudated by planktonic diatoms maintained in batch cultures

Abstract Axenic cultures of the marine planktonic diatoms Navicula directa (W. Smith) Ralfs, Amphora holsatica Hustedt and Melosira nummuloides (Dillwyn) Agardh, isolated from samples from the Ria de Aveiro, Portugal, were successfully established. For each culture, the extracellular carbohydrate production was related to the growth curve and nutrient concentration (NO3– and PO43–) in the culture medium. Analysis by gas-liquid chromatography and Fourier transform infrared spectroscopy (FT-IR) was performed on the exopolysaccharides isolated from the culture medium. It was concluded that the three marine diatoms produced and exudated different amounts of carbohydrates, and that the exudation process was more important when the media were almost nutrient depleted, and also when the species reached the stationary growth phase. The exopolysaccharides produced by the three species, mainly polymers of uronic acids, were very similar. However, the results obtained from gas-liquid chromatography suggest that differences in the composition of neutral sugars may occur. The FT-IR spectra support the results of chemical analysis.

Short-term dynamics in microphytobenthos distribution and associated extracellular carbohydrates in surface sediments of an intertidal mudflat

Two field studies were conducted to study the in situ net production of extracellular carbohydrates and the distribution of benthic diatoms over a period of 24 h per study. A comparison was made between a situation where a clear surface biofilm of diatoms had developed and a situation where this was not the case, Vertical profiles were made by sampling the top 2 mm of the sediment at depth intervals of 0.2 mm using the 'cryolander' technique. In the presence of a biofilm, diatom distribution showed a consistent pattern when the sediment was emersed. In the light, most of the diatoms were present in the top 0.2 mm while in the dark, diatoms were homogeneously distributed in the upper 2 mm of the sediment. When a biofilm was absent, no clear patterns were observed. Extracellular carbohydrates were extracted from the sediment and separated in 2 operationally defined fractions (colloidal and EDTA- extractable). The 2 carbohydrate fractions showed a different dynamic behaviour. The colloidal carbohydrate fraction was highly variable while the EDTA-extractable fraction behaved more conservatively. Only in the light and in the presence of a diatom biofilm, was production of extracellular carbohydrates observed, The maximum rate of chlorophyll-normalized production of extracellular carbohydrates, expressed in glucose equivalents (g g(-1)), amounted to 20 h(-1) in the upper 0.2 mm. The molecular size distribution of both carbohydrate fractions was similar. The monosaccharide composition was also similar, except that the EDTA-extractable fraction contained a higher percentage of uronic acids, Carbohydrates produced during tidal emersion were rich in glucose and were rapidly turned over. [KEYWORDS: extracellular polymeric substances (EPS); polysaccharides; microphytobenthos; mud flat; monosaccharide composition; cryolander Polysaccharide hydrolysis rates; benthic microalgae; marine-sediments; epipelic diatoms; cohesive sediments; organic-carbon; chlorophyll-a; environments; assemblages; irradiance]

The effect of pH on growth rate, biochemical composition and extracellular carbohydrate production of the marine diatom Skeletonema costatum

The marine diatom Skeletonema costatum was grown at different pH values in a semicontinuous cultivation system which kept the pH at a pre-set value. Growth rate was nearly constant at pH 6·5–8·5 (average 2·4 divisions day−1) and declined at pH > 9. Organic carbon (C) production decreased from an average of 5·3 mg l−1 at pH 6·5–8·5 to 2 and 1 mg l−1 at pH 9·0 and 9·4, respectively. Storage β-1,3-linked glucan decreased from a high of 7·1 mg l−1 at pH 6·5 to 0·2 mg l−1 at pH 9·4, and, concomitantly, the percentage of total organic C as glucan C decreased from 60% to 10%. Cellular concentration of amino acids varied from about 62 to 8 mM over the pH range 8·0–9·4. At pH 9·4 the concentration of glutamine was below the detection limit. The extracellular production of carbohydrates in the pH range 6·5–8·5 was only 3·7% (average) of total C production and increased at pH 9·0 and 9·4. The decrease in growth rate at pH > 9·0 might be caused by a decrease in the rate of some important biochemical reactions, as well as by a change in cell membrane properties in this pH range.

The effect of pH on growth rate, biochemical composition and extracellular carbohydrate production of the marine diatom Skeletonema costatum

The marine diatom Skeletonema costatum was grown at different pH values in a semicontinuous cultivation system which kept the pH at a pre-set value. Growth rate was nearly constant at pH 6·5–8·5 (average 2·4 divisions day−1) and declined at pH > 9. Organic carbon (C) production decreased from an average of 5·3 mg l−1 at pH 6·5–8·5 to 2 and 1 mg l−1 at pH 9·0 and 9·4, respectively. Storage β-1,3-linked glucan decreased from a high of 7·1 mg l−1 at pH 6·5 to 0·2 mg l−1 at pH 9·4, and, concomitantly, the percentage of total organic C as glucan C decreased from 60% to 10%. Cellular concentration of amino acids varied from about 62 to 8 mM over the pH range 8·0–9·4. At pH 9·4 the concentration of glutamine was below the detection limit. The extracellular production of carbohydrates in the pH range 6·5–8·5 was only 3·7% (average) of total C production and increased at pH 9·0 and 9·4. The decrease in growth rate at pH > 9·0 might be caused by a decrease in the rate of some important biochemical reactions, as well as by a change in cell membrane properties in this pH range.

The production of extracellular carbohydrates by estuarine benthic diatoms: the effects of growth phase and light and dark treatment

Epipelic diatoms are important constituents of estuarine microphytobenthic biofilms. Field‐based investigations have shown that the production of carbohydrates by such taxa is ecologically important. However, limited information exists on the dynamics of carbohydrate production by individual species of epipelic diatoms. The production of low and high molecular weight extracellular carbohydrates in axenic cultures of five species of benthic estuarine diatoms, Cylindrotheca closterium (Ehrenberg), Navicula perminuta (Grun.) in Van Heurck, Nitzschia frustulum (Kütz.) Grunow, Nitzschia sigma (Kütz.) Grunow, and Surirella ovata (Kütz.) Grunow, were investigated. All species produced colloidal (water‐soluble) carbohydrates during growth, with maximal production occurring during stationary phase. During logarithmic growth, approximately 20% of extracellular carbohydrates consisted of polymeric material (extracellular polymeric substances [EPS]), but during stationary phase, EPS content increased to 34%–50%. Pyrolysis–mass spectrophotometry analysis showed differences in the composition of EPS produced during logarithmic and stationary phase. All species synthesized glucan as a storage carbohydrate, with maximum glucan accumulation during the transition from log to stationary phase. Short‐term labeling with 14C‐bicarbonate found that between 30 and 60% of photoassimilates were released as colloidal carbohydrate, with EPS consisting of approximately 16% of this colloidal fraction. When cells were placed in darkness, EPS production increased, and between 85 and 99% of extracellular carbohydrate produced was polymeric. Glucan reserves were utilized in dark conditions, with significant negative correlations between EPS and glucan for N. perminuta and S. ovata. Under dark conditions, cells continued to produce EPS for up to 3 days, although release of low molecular weight carbohydrates rapidly ceased when cells were dark treated. Three aspects of EPS production have been identified during this investigation: (1) production during rapid growth, which differs in composition from (2) EPS directly produced as a result of photosynthetic overflow during growth limiting conditions and (3) EPS produced for up to 3 days in the dark using intracellular storage reserves (glucans). The ecological implications of these patterns of production and utilization are discussed.

Influence of nutrient ratios on the in vitro extracellular polysaccharide production by marine diatoms from the Adriatic Sea

Three different species of marine diatoms, <it>Nitzschia closterium</it> (Ehr) Smith, <it>Chaetoceros</it> sp. (Ehr) and <it>Skeletonema costatum</it> (Grev) Cleve, were isolated from the Adriatic sea and studied <it>in vitro</it> for the production of extracellular carbohydrates. Variations of the nitrogen (N)/phosphorus (P)/silicon (Si) ratios in the growth medium affect the accumulation and release of carbohydrates. In the<it>N.closterium</it> cultures at high N/P ratio, the rate of extracellular polysaccharide release was higher both in rapidly growing cells (2.14 <IMG SRC="/math/mu.gif">g per 10⁶ cells day^-1 and in stationary phase (1.0 &mgr;g per 10⁶ cells day^-1) compared to <it>S.costatum</it> and <it>Chaetoceros</it> sp. Instead, at low N/P ratios, <it>S.costatum</it> and<it>Chaetoceros</it> sp. produced large amounts of extracellular polysaccharides during the logarithmic phase, compared to<it>N.closterium</it>, with values of 10 &mgr;g per 10⁶ cells day^-1 for<it>S.costatum</it> and 2.8 &mgr;g per 10⁶ cells day^-1 for<it>Chaetoceros</it> sp., respectively; in particular, only<it>S.costatum</it> was able to produce extracellular carbohydrates (1.2 &mgr;g per 10⁶ cells day^-1) during the stationary phase of growth. Under Si limitation, any of the three diatom species produce extracellular polysaccharides both in the logarithmic and stationary phase of growth. The potential ecological significance of these findings is discussed.

Hydraulic conductivity in soils irrigated with wastewaters of differing strengths: Field and laboratory studies

Application of wastewater can decrease the hydraulic conductivity of soils, and so reduce future loading rates. A possible mechanism for this decrease is blockage of soil pores by microbial growth and extracellular carbohydrate production. Our objective was to determine whether wastewater characteristics that increased microbial biomass and carbohydrate also decreased soil hydraulic conductivity. In field trials, irrigation of secondary-treated wastewater for 7 years onto a sandy soil increased carbohydrate, but had no effect on microbial C or unsaturated hydraulic conductivity, relative to non-irrigated soil. Irrigation of tertiary-treated wastewater for 5 years onto an allophanic soil had no significant effect on these soil characteristics. Effects on soil properties of wastewater with differing carbon : nitrogen (C : N) ratio were examined in the laboratory on repacked cores of the allophanic soil over 14 weeks. Unsaturated hydraulic conductivity decreased significantly in cores irrigated with the high C: N wastewater. These cores also exhibited an increase in soil carbohydrate content, microbial biomass, and respiration relative to cores irrigated with water. This study has demonstrated that the land treatment of industrial wastewaters of high C: N ratio and high biochemical oxygen demand could be problematic, even on freely draining soils.

A staining technique for attached bacteria and its correlation to extracellular carbohydrate production

Bacterial extracellular polysaccharides have been shown to be involved in the attachment process of cell to solid substratum. The method described here permits study of polysaccharides and their association with the substrate surface, using a novel staining technique for light microscopy. The method can be applied both in the laboratory and in situ and appears to be independent of polysaccharide composition and structure.

Extracellular carbohydrate liberation in the flagellatesIsochrysis galbanaandPrymnesium parvum

The production of extracellular carbohydrate has been studied inIsochrysis galbanaandPrymnesium parvumin axenic culture. Increased extracellular production of carbohydrate occurred at reduced and increased salinity, low light intensity and under conditions of nitrogen starvation inIsochrysis, and in some cases appeared to be associated with the sedimentation of the cells from stagnant culture. Extracellular carbohydrate production was found to be greatest during the early and later stages in growth and dropped to a minimum during the mid-growth phase. Experiments indicated that the cells were not being damaged during harvesting of the cultures. A close similarity was found between the monosaccharide components of the intra- and extracellular carbohydrate after acid hydrolysis; both contained glucose, galactose, arabinose, xylose and ribose. It is suggested that the production of most of the extracellular carbohydrate is due to the passive release of organic matter from dead or dying cells.

The Production of Extracellular Carbohydrates by Some Marine Flagellates1

Extracellular carbohydrate production during the growth of bacteria‐free cultures of the marine flagellates Isochrysis galbana, Monochrysis lutheri, Prymnesium parvum, Dunaliella euchlora, Pyraminomonas sp., Rhodomonas (?) sp., and Chlamydomonas sp. was followed by the N‐ethyl carbazole method.Carbohydrate production did not parallel cell numbers during exponential growth of any of these organisms; maximum concentrations during this phase were under 3 mg/L. Carbohydrates accumulated in all stationary cultures (having 106–107 cells/ml), to the greatest extent in Prymnesium cultures, which attained 123 mg/L. Isochrysis and Monochrysis produced 25 and 16 mg/L, respectively, while the others had under 10 mg/L even when cell disintegration was evident.Aging cultures (not all bacteria‐free) of 4 diatoms, 2 dinoflagellates, 2 additional green algae, and a cyanophyte were assayed. Concentrations ranged from 1.5 to 60 mg/L.This suggests that the organisms studied contribute significant free carbohydrates only during late bloom conditions, when algae are abundant and under physiological circumstances resembling stationary or declining culture.