Rhodospira trueperi gen. nov., spec. nov., a new phototrophic Proteobacterium of the alpha group

A new phototrophic purple bacterium was isolated from a flat, laminated microbial mat in a salt marsh near Woods Hole, Mass., USA. The spiral-shaped bacterium was highly motile and had bipolar tufts of flagella and intracytoplasmic membranes of the vesicular type. The major photosynthetic pigments were identified as the carotenoid tetrahydrospirilloxanthin and bacteriochlorophyll b. The long wavelength in vivo absorption maximum of the bacteriochlorophyll was at 986 nm. The marine bacterium showed optimal growth in the presence of 2% NaCl. It utilized a number of organic substrates as carbon and energy sources and required vitamins and sulfide as a reduced sulfur source for growth. In the presence of sulfide, elemental sulfur globules were formed outside the cells. Elemental sulfur was not further oxidized to sulfate. The new isolate had a unique lipid and fatty acid composition, and according to the 16S rRNA gene sequence, it is most similar to Rhodospirillum rubrum. It is described as a new species and assigned to a new genus with the proposed name Rhodospira trueperi. Received: 16 September 1996 / Accepted: 24 January 1997     

On the mechanism of glycolate synthesis by Chromatium and Chlorella

When cultures of the photosynthetic bacterium, Chromatium vinosum, capable of photosynthesizing glycolate at about 10 μmol/mg of bacteriochlorophyll/h were exposed to atmospheres enriched with ¹⁸O₂, one atom of oxygen-18 was incorporated into the car?yl group of glycolate. Allowing for the small (3–5%) loss of oxygen-18 during the manipulations leading up to the mass spectrometric determination of the oxygen-18 content of the glycolate, the isotopic enrichment of the¹⁸O-labeled glycolate synthesized by Chromatium was substantially (at least 94%) the same as the isotopic enrichment of the ¹⁸O₂. Similar results were obtained with the green alga, Chlorella fusca. The close agreement between the isotopic enrichments of the glycolate and the oxygen with which it was synthesized was independent of the oxygen concentration. The major pathway of glycolate synthesis by Chromatium therefore involves reaction(s) which bring about the incorporation of one atom of molecular oxygen into the car?yl group of glycolate. The in vitro rate of ribulose 1,5-bisphosphate oxygenase in extracts of Chromatium, previously thought to be too low to account for the rates of glycolate synthesis in vivo, was shown to be adequate for this purpose when precautions were taken to fully activate the enzyme. Similarly, the activity of phosphoglycolate phosphatase, when assayed under optimal conditions, was also adequate to sustain the rates of glycolate formation observed i vivo. It is concluded that the oxygenolytic cleavage of ribulose 1,5-bisphosphate represents the major pathway of glycolate synthesis by Chromatium.     

Thiocapsa halophila sp. nov., a new halophilic phototrophic purple sulfur bacterium

A new phototrophic sulfur bacterium has been isolated from a red layer in a laminated mat occurring underneath a gypsum crust in the mediterranean salterns of Salin-de-Giraud (Camargue, France). Single cells were coccus-shaped, non motile, without gas vacuoles and contained sulfur globules. Bacteriochlorophyll a and okenone were present as major photosynthetic pigments. These properties and the G+C content of DNA (65.9–66.6 mol% G+C) are typical characteristics of the genus Thiocapsa. However, the new isolate differs from known species in the genus, particularly in NaCl requirement (optimum, 7% NaCl; range, 3–20% NaCl) and some physiological characteristics. Therefore, a new species is proposed, Thiocapsa halophila, sp. nov.Dedicated to Prof. Dr. Norbert Pfennig in occasion of his 65th birthday     

Thiorhodococcus minus, gen. nov., sp. nov., a new purple sulfur bacterium isolated from coastal lagoon sediments

A new marine phototrophic purple sulfur bacterium (strain CE2203) was isolated in pure culture from a man-made coastal lagoon located on the Atlantic coast (Arcachon Bay, France). Single cells were coccus-shaped, did not contain gas vesicles, and were highly motile. Intracellular photosynthetic membranes were of the vesicular type. Bacteriochlorophyll a and carotenoids of the normal spirilloxanthin series were present as photosynthetic pigments. Hydrogen sulfide, thiosulfate, elemental sulfur, and molecular hydrogen were used as electron donors during photolithotrophic growth under anoxic conditions, while carbon dioxide was utilized as carbon source. Acetate, propionate, lactate, glycolate, pyruvate, fumarate, succinate, fructose, sucrose, ethanol, and propanol were photoassimilated in the presence of hydrogen sulfide. During growth on sulfide, elemental sulfur globules were stored inside the cells. Chemotrophic growth under microoxic conditions in the dark was possible. The DNA base composition was 66.9 mol% G+C. Comparative sequence analysis of the 16S rRNA gene confirmed the membership of strain CE2203 in the family Chromatiaceae. Morphological characteristics of strain CE2203 indicated a close affiliation to the genera Thiocystis and Thiocapsa. However, the phylogenetic treeing revealed no closer relationship to Thiocystis spp. than to Thiocapsa roseopersicina or other known members of the Chromatiaceae. Consequently, strain CE2203 is proposed as the type strain of a new genus and species, Thiorhodococcus minus gen. nov., sp. nov. Received: 23 December 1996 / Accepted: 27 March 1997     

<Emphasis Type="Italic">Thiocapsa imhoffii</Emphasis>, sp. nov., an alkaliphilic purple sulfur bacterium of the family <Emphasis Type="Italic">Chromatiaceae</Emphasis> from Soap Lake,Washington (USA)

An alkaliphilic purple sulfur bacterium, strain SC5, was isolated from Soap Lake, a soda lake located in east central Washington state (USA). Cells of strain SC5 were gram-negative, non-motile, and non-gas vesiculate cocci, often observed in pairs or tetrads. In the presence of sulfide, elemental sulfur was deposited internally. Liquid cultures were pink to rose red in color. Cells contained bacteriochlorophyll a and spirilloxanthin as major photosynthetic pigments. Internal photosynthetic membranes were of the vesicular type. Optimal growth of strain SC5 occurred in the absence of NaCl (range 0–4%), pH 8.5 (range pH 7.5–9.5), and 32°C. Photoheterotrophic growth occurred in the presence of sulfide or thiosulfate with only a limited number of organic carbon sources. Growth factors were not required, and cells could fix N₂. Dark, microaerobic growth occurred in the presence of both an organic carbon source and thiosulfate. Sulfide and thiosulfate served as electron donors for photoautotrophy, which required elevated levels of CO₂. Phylogenetic analysis placed strain SC5 basal to the clade of the genus Thiocapsa in the family Chromatiaceae with a 96.7% sequence similarity to its closest relative, Thiocapsa roseopersicina strain 1711^T (DSM217^T). The unique assemblage of physiological and phylogenetic properties of strain SC5 defines it as a new species of the genus Thiocapsa, and we describe strain SC5 herein as Tca. imhoffii, sp. nov.     

Development of a phosphate-removal system using a marine photosynthetic bacterium Chromatium sp.

The marine photosynthetic bacterium Chromatium sp. successfully removed orthophosphate when grown phototrophically. The phosphate-uptake rate was almost constant at more than 5.0 mg- PO₄ ³⁻/l in synthetic medium. Addition of seawater causes flocculation of this strain. The successful use of seawater as an inexpensive source of magnesium could prove to be effective in the removal of photosynthetic bacterial cells from a medium. A semicontinuous culture system was used for the removal of low concentrations of phosphate and the phosphate-uptake activity of Chromatium sp. was maintained under 0.1 day⁻¹ dilution rate. This strain was also able to remove high concentrations of phosphate from domestic sewage. Received 24 May 1996 / Received revision: 5 August 1996 / Accepted: 6 September 1996     

Ectothiorhodospira marismortui sp. nov., an obligately anaerobic,moderately halophilic purple sulfur bacterium from a hypersaline sulfur spring on the shore of the Dead Sea

A novel type of purple sulfur bacterium was isolated from a hypersaline sulfur spring on the shore of the Dead Sea. The cells of the isolate are irregularly rod-shaped or curved, and motile by means of a tuft of polar flagella. The photosynthetic system, containing bacteriochlorophyll a and carotenoids of the spirilloxanthin series, is located on stacks of lamellar membranes in the cell cytoplasm. The organism can grow either photoautotrophically with sulfide as electron donor, which is oxidized via extracellular sulfur to sulfate, or photoheterotrophically, using acetate, succinate, fumarate, malate or pyruvate as carbon sources. The bacterium is obligately anaerobic, and requires a source of reduced sulfur for growth. The isolate is moderately halophilic, and grows optimally at NaCl concentrations between 3 and 8%, temperatures between 30 and 45°C, and neutral pH. 16S ribosomal RNA oligonucleotide cataloging suggests a close relationship to purple sulfur bacteria of the genus Ectothiorhodospira. As the isolate differs greatly from the described members of the genus Ectothiorhodospira, we describe the isolate as a new species, and propose the name Ectothiorhodospira marismortui sp. nov.     

Regulation of nitrogenase activity by covalent modification in Chromatium vinosum

Nitrogenase in Chromatium vinosum was rapidly, but reversibly inhibited by NH ₄ ⁺ . Activity of the Fe protin component of nitrogenase required both Mn²⁺ and activating enzyme. Activating enzyme from Rhodospirillum rubrum could replace Chromatium chromatophores in activating the Chromatium Fe protein, and conversely, a protein fraction prepared from Chromatium chromatophores was effective in activating R. rubrum Fe protein. Inactive Chromatium Fe protein contained a peptide covalently modified by a phosphate-containing molecule, which migrated the same in SDS-polyacrylamide gels as the modified subunit of R. rubrum Fe protein. In sum, these observations suggest that Chromatium nitrogenase activity is regulated by a covalent modification of the Fe protein in a manner similar to that of R. rubrum.Abbreviation HEPES N-2-hydroxyethyl piperazine-N-2-ethanesulfonic acid     

Evaluating the Potential of Halothiobacillus Bacteria for Sulfur Oxidation and Biomass Production under Saline Soil

Abstract

Salinity negatively affects growth of sulfur-oxidizing bacteria (SOB) and their sulfate production ability, meanwhile decreases the available sulfate for plants in soil. The aim of this study was to isolate and characterize the bacteria of genus Halothiobacillus, as a salt-tolerant SOB, from saline and sulfidic habitats of Iran for the first time and evaluating the effect of salinity on their biomass and sulfate production during the oxidation of different sulfur sources. Isolation process and surveying the morphological, biochemical and 16S rRNA gene analysis resulted into identification of three species (eight strains) of Halothiobacillus genus including H. neapolitanus, H. hydrothermalis and H. halophilus. Salinity (0, 0.5, 1, 2 and 4?M NaCl) had a significant impact (p?≤?0.01) on bacterial biomass and sulfate production during the oxidation of thiosulfate and elemental sulfur. Biomass and sulfate production by strains was accompanied by a decrease in residual content of thiosulfate (RCT) in medium. The amount of produced biomass and sulfate in medium supplemented by thiosulfate was much higher than elemental sulfur. The highest amount of biomass and sulfate was produced by H. neapolitanus strain I19 at 0.5 and 1?M NaCl concentration. The results of this study could be the first step to focus on the application of these bacteria to increase sulfate storage of saline soils and crop production.     

A heterotrophic bacterium inhibits growth of several species of the genus Chlorobium

A gram-negative bacterium (designed as strain BF 9500) causing growth inhibition zones on cell lawns of the anoxygenic phototrophic bacterium Chlorobium limicola BF 8000 was isolated from Lake Cisó (Spain). Strain BF 9500, identified as Stenotrophomonas maltophilia, caused growth inhibition zones on cell lawns of several strains of C. limicola except C. limicola DSM 245. It also inhibited other Chlorobium species and several heterotrophic bacteria. However, it had no effect on the growth of the eleven strains of Chromatiaceae tested. Strain BF 9500 caused the lysis of C. limicola BF 8000, whose cells formed “ghosts”. To date, this is the first report of a bacterium causing the lysis of species of the genus Chlorobium. Received: 15 August 1996 / Accepted: 15 January 1997     

The fine structure of Chromatium buderi

Summary The fine structure of the phototrophic sulfur bacterium Chromatium buderi was studied in ultrathin sections and freeze-etch preparations.In addition to an intracytoplasmic membrane system common to all species of the Chromatiaceae, C. buderi contained extended lamellar membrane structures possibly due to too high light intensities during growth. The cell wall of C. buderi was found to be covered by a honeycomb-like outer layer consisting of macromolecular wine-glass shaped subunits 60–80 nm by 60 nm in size. This outer cell wall layer appears to be a typical property of the large cell Chromatium species.Contribution No. 3008 of the Woods Hole Oceanographic Institution.     

Complete assimilation of cysteine by a newly isolated non-sulfur purple bacterium resembling Rhodovulum sulfidophilum (Rhodobacter sulfidophilus)

A rod-shaped, motile, phototrophic bacterium, strain SiCys, was enriched and isolated from a marine microbial mat, with cysteine as sole substrate. During phototrophic anaerobic growth with cysteine, sulfide was produced as an intermediate, which was subsequently oxidized to sulfate. The molar growth yield with cysteine was 103 g mol^–1, in accordance with complete assimilation of electrons from the carbon and the sulfur moiety into cell material. Growth yields with alanine and serine were proportionally lower. Thiosulfate, sulfide, hydrogen, and several organic compounds were used as electron donors in the light, whereas cystine, sulfite, or elemental sulfur did not support phototrophic anaerobic growth. Aerobic growth in the dark was possible with fructose as substrate. Cultures of strain SiCys were yellowish-brown in color and contained bacteriochlorophyll a, spheroidene, spheroidenone, and OH-spheroidene as major photosynthetic pigments. Taking the morphology, photosynthetic pigments, aerobic growth in the dark, and utilization of sulfide for phototrophic growth into account, strain SiCys was assigned to the genus Rhodovulum (formerly Rhodobacter) and tentatively classified as a strain of R. sulfidophilum. In cell-free extracts in the presence of pyridoxal phosphate, cysteine was converted to pyruvate and sulfide, which is characteristic for cysteine desulfhydrase activity (l-cystathionine γ-lyase, EC 4.4.1.1). Received: 15 December 1995 / Accepted: 1 April 1996     

Selective enrichment and characterization of Roseospirillum parvum, gen. nov. and sp. nov., a new purple nonsulfur bacterium with unusual light absorption properties

A new type of phototrophic purple bacterium, strain 930I, was isolated from a microbial mat covering intertidal sandy sediments of Great Sippewissett Salt Marsh (Woods Hole, Mass., USA). The bacterium could only be enriched at a wavelength of 932 (± 10) nm. Cells were vibrioid- to spirilloid-shaped and motile by means of bipolar monotrichous flagellation. The intracytoplasmic membranes were of the lamellar type. Photosynthetic pigments comprised bacteriochlorophyll a and the carotenoids spirilloxanthin and lycopenal. The isolated strain exhibited an unusual, long-wavelength absorption maximum at 911 nm. Sulfide or thiosulfate served as electron donor for anoxygenic phototrophic growth. During growth on sulfide, elemental sulfur globules formed outside the cells. Elemental sulfur could not be further oxidized to sulfate. In the presence of sulfide plus bicarbonate, fructose, acetate, propionate, butyrate, valerate, 2-oxoglutarate, pyruvate, lactate, malate, succinate, fumarate, malonate, casamino acids, yeast extract, L(+)-alanine, and L(+)-glutamate were assimilated. Sulfide, thiosulfate, or elemental sulfur served as a reduced sulfur source for photosynthetic growth. Maximum growth rates were obtained at pH 7.9, 30 °C, 50 μmol quanta m^–2 s^–1 of daylight fluorescent tubes, and a salinity of 1–2% NaCl. The strain grew microaerophilically in the dark at a partial pressure of 1 kPa O₂. The DNA base composition was 71.2 mol% G + C. Sequence comparison of 16S rRNA genes indicated that the isolate is a member of the α-Proteobacteria and is most closely related to Rhodobium orientis at a similarity level of 93.5%. Because of the large phylogenetic distance to known phototrophic species of the α-Proteobacteria and of its unique absorption spectrum, strain 930I is described as a new genus and species, Roseospirillum parvum gen. nov. and sp. nov. Received: 29 December 1998 / Accepted: 17 March 1999     

Sulfonates: novel electron acceptors in anaerobic respiration

The enrichment and isolation in pure culture of a bacterium, identified as a strain of Desulfovibrio, able to release and reduce the sulfur of isethionate (2-hydroxyethanesulfonate) and other sulfonates to support anaerobic respiratory growth, is described. The sulfonate moiety was the source of sulfur that served as the terminal electron acceptor, while the carbon skeleton of isethionate functioned as an accessory electron donor for the reduction of sulfite. Cysteate (alanine-3-sulfonate) and sulfoacetaldehyde (acetaldehyde-2-sulfonate) could also be used for anaerobic respiration, but many other sulfonates could not. A survey of known sulfate-reducing bacteria revealed that some, but not all, strains tested could utilize the sulfur of some sulfonates as terminal electron acceptor. Isethionate-grown cells of Desulfovibrio strain IC1 reduced sulfonate-sulfur in preference to that of sulfate; however, sulfate-grown cells reduced sulfate-sulfur in preference to that of sulfonate. Received: 2 May 1996 / Accepted: 8 June 1996     

Solitary terminal cells of Aphanizomenon gracile (Cyanobacteria,Nostocales) can divide and renew trichomes

An attempt was made to find evidence that morphologically distinct terminal cells of filamentous cyanobacterium Aphanizomenon gracile strain CCALA 8 are capable of dividing and forming trichomes. Based on our current knowledge, the division of morphologically diversified terminal cells is possible in nostocalean cyanobacteria. However, this process has been observed only in a few species. Terminal cells of A. gracile differ morphologically from other vegetative cells of a trichome, as they are not hyaline and can sometimes be found as solitary cells in cultures. Hence, it was reasonable for us to suspect that these cells are capable of dividing and forming trichomes. We observed terminal cells under a light and transmission electron microscope. Microscopic observations revealed that the septum formed in both solitary terminal cells and in terminal cells attached to trichomes. Our study is the first to demonstrate division and renewal of trichomes in terminal cells of A. gracile. Previously, such mode of reproduction was described only for another nostocalean cyanobacterium Raphidiopsis mediterranea. Moreover, our findings further emphasize the variability among members that belong to the genus Aphanizomenon , in which a type species (A. flos‐aquae) has hyaline cells incapable of dividing and renewing trichomes, while A. gracile can additionally propagate by solitary terminal cells division. This additional feature distinguishing A. gracile from typical species of Aphanizomenon, such as A. flos‐aquae, might be valuable for resolving taxonomic position of the species considering ambiguous genetic relationship between A. gracile and A. flos‐aquae.     

Desulforhopalus vacuolatus gen. nov., sp. nov., a new moderately psychrophilic sulfate-reducing bacterium with gas vacuoles isolated from a temperate estuary

A new type of gas-vacuolated, sulfate-reducing bacterium was isolated at 10° C from reduced mud (E₀ < 0) obtained from a temperate estuary with thiosulfate and lactate as substrates. The strain was moderately psychrophilic with optimum growth at 18–19° C and a maximum growth temperature of 24° C. Propionate, lactate, and alcohols served as electron donors and carbon sources. The organism grew heterotrophically only with hydrogen as electron donor. Propionate and lactate were incompletely oxidized to acetate; traces of lactate were fermented to propionate, CO₂, and possibly acetate in the presence of sulfate. Pyruvate was utilized both with and without an electron acceptor present. The strain did not contain desulfoviridin. The G+C content was 48.4 mol%. The differences in the 16S rRNA sequence of the isolate compared with that of its closest phylogenetic neighbors, bacteria of the genus Desulfobulbus, support the assignment of the isolate to a new genus. The isolate is described as the type strain of the new species and genus, Desulforhopalus vacuolatus. Received: 4 March 1996 / Accepted: 17 June 1996     

Chromatium buderi nov. spec., eine neue Art der “großen” Thiorhodaceae

Zusammenfassung Aus Salzschlamm von der Galapagos-Insel Santa Cruz sowie Salzmarschen bei Barnstable (Cape Cod, Mass.) wurde ein Schwefelpurpurbakterium isoliert, das aufgrund seiner Morphologie, Pigmentausrüstung und Physiologie als neue Art beschrieben wird: Chromatium buderi nov. spec. Der Organismus ist als grßes Chromatium anzusehen und wird gegen die anderen großen Chromatien C. okenii, C. weissei und C. warmingii abgegrenzt.

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Chromatium buderi nov. spec., a new species of the large Thiorhodaceae

Summary A new Thiorhodaceae species belonging to the large types of the genus Chromatium was isolated from an estuarine salt flat on Santa Cruz, Galapagos Islands, as well as from the Barnstable salt marshes, Cape Cod., Mass. The new species, Chromatium buderi, is described and differentiated from C. okenii, C. weissei and C. warmingii.

     

Die Verwertung einfacher organischer Substrate durch Thiorhodaceae

Zusammenfassung Es wurden 22 Gram-negative, Bacteriochlorophyll a enthaltende Stämme der Thiorhodaceae auf die Fähigkeit untersucht, verschiedene anorganische und organische Verbindungen als Wasserstoff-Donatoren und gegebenenfalls als Kohlenstoff-Quelle in Gegenwart von Bicarbonat und einer geringen Menge Sulfid als Reduktionsmittel und Schwefelquelle anaerob im Licht zu nutzen.Allen geprüften Stämmen ist die Eigenschaft gemeinsam, mit Sulfid, elementarem Schwefel, Acetat und Pyruvat zu wachsen.Mit Thiosulfat können Chromatium warmingii, Chromatium weissei, Chromatium okenii und zwei Thiocystis-Stämme nicht wachsen.Malat, Succinat und Fumarat werden von Stamm D-ähnlichen Chromatien, Thiocapsa floridana und einem Thiocystis-Stamm verwertet.Fettsäure (ab drei C-Atomen) können von den meisten Stämmen nicht genutzt werden. Viele Stämme werden insbesondere durch die höheren Fettsäuren im Wachstum gehemmt.Von den Zuckern erwiesen sich nur Glucose und Fructose bei wenigen Stämmen als geeignetes Substrat.Methanol und Äthanol werden nicht verwertet. Propanol wird durch einen Thiocystis-Stamm und Glycerin durch alle Thiocapsa-Stämme genutzt.Die Ergebnisse werden hinsichtlich ihrer taxonomischen Bedeutung diskutiert.

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Assimilation of simple organic compounds by Thiorhodaceae

Summary Twenty two gram-negative bacteriochlorophyll a containing strains of Thiorhodaceae were examined for the ability to utilize various inorganic compounds as hydrogen donors. Various organic compounds were tested for their ability to serve as both hydrogen donor and carbon source. A small amount of sulfide was employed as both reduction agent and sulfur source. all experiments were conducted in the presence of bicarbonate.All strains could be grown on one of the following substances: sulfide, elemental sulfur, acetate, or pyruvate.With thiosulfate Chromatium warmingii, Chromatium weissei, Chromatium okenii and two strains of Thiocystis could not grow.Malate, succinate and fumarate were used by several strains of Chromatium similar to strain D as well as by Thiocapsa floridana and one strain of Thiocystis.Fatty acids with three or more carbon atoms were not utilized by most strains; in addition, many strains were inhibited by the higher fatty acids.A few strains could grow on glucose or fructose. Methanol and ethanol were not utilized. One strain of Thiocystis could utilize propanol. All Thiocapsa strains could grow on glycerol.The results were discussed with respect to their significance to the taxonomy of Thiorhodaceae.

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Diese Arbeit wurde durch Forschungsmittel des Landes Niedersachsen und des Bundesministeriums für wissenschaftliche Forschung gefördert.     

The role of phototrophic sulfur bacteria as food for meiobenthic harpacticoid copepods inhabiting eutrophic coastal lagoons

Laboratory experiments were undertaken using Amonardia normani and Schizopera cf. compacta, two meiobenthic harpacticoid copepods commonly found in coastal lagoons. The first experiments were designed to determine if the phototrophic sulfur bacteria Chromatium gracile can be ingested by these copepods and at what concentrations. Egestion rate was used as an index of feeding rate. The response of the egestion rate, expressed in numbers of faecal pellets produced by copepod per day, as a function of bacterial concentration followed the functional model. A. normani attained constant feeding rates from the bacterial concentration of 1 × 10⁷ cells ml^–1 (5 µg C ml^–1) onwards, S. cf. compacta attained constant feeding rates from 2.6 × 10⁷ cells ml^–1 (13 µg C ml^–1) onwards. The faecal pellet volume changed significantly (p<0.05) between food concentrations for A. normani but not for S. cf. compacta (p>0.05). In order to investigate the effect of the phototrophic bacterial diet on the population dynamics of A. normani three groups of nauplii were maintained at 2 × 10⁷ cells ml^–1 and observed every day. The mortality of these nauplii was very high compared to those maintained on a diatom diet (Nitzschia constricta); only in one of the groups did some copepodites develop but no adults were ever observed. Adults fed on bacteria did not have different (p>0.05) survival rates compared to those fed on diatoms, nevertheless, the number of nauplii produced was significantly less (p<0.05) on the bacterial diet. These results lead us to suggest that although the phototrophic sulfur bacteria (Chromatium gracile) can be ingested by both copepod species it cannot sustain the full development of the A. normani population. Thus, a bloom of phototrophic sulfur bacteria does not seem to be a favourable situation for opportunistic benthic copepods to colonize eutrophic coastal lagoons after a dystrophic crisis.