The influence of protozoa with a filtered and non-filtered seawater culture of Tetraselmis sp., and effects to the bacterial and algal communities over 10 days

In this study a filter was used to remove protozoa and its effects on a Tetraselmis sp. culture were evaluated in terms of final total lipid, final total dry weight, cell counts, and both the bacterial and algal communities. The protozoa species observed within this study was identified as Cohnilembus reniformis. It was observed that on the final day no C. reniformis were present in filtered cultures compared to the non-filtered culture which contained 40±3 C. reniformis/mL. The presence of C. reniformis within the culture did not affect the total lipid or the total dry weight recovered, suggesting that Tetraselmis sp. was capable of surviving and growing in the presence of C. reniformis. Overall it is suggested that an 11 μm filter was effective at removing protozoa, though growing a microalgae culture without filtration did not show any significant effect.

Characterization of phototrophic purple nonsulfur bacteria forming colored microbial mats in a swine wastewater ditch

The community structure of pink-colored microbial mats naturally occurring in a swine wastewater ditch was studied by culture-independent biomarker and molecular methods as well as by conventional cultivation methods. The wastewater in the ditch contained acetate and propionate as the major carbon nutrients. Thin-section electron microscopy revealed that the microbial mats were dominated by rod-shaped cells containing intracytoplasmic membranes of the lamellar type. Smaller numbers of oval cells with vesicular internal membranes were also found. Spectroscopic analyses of the cell extract from the biomats showed the presence of bacteriochlorophyll a and carotenoids of the spirilloxanthin series. Ubiquinone-10 was detected as the major quinone. A clone library of the photosynthetic gene, pufM, constructed from the bulk DNA of the biomats showed that all of the clones were derived from members of the genera Rhodobacter and Rhodopseudomonas. The dominant phototrophic bacteria from the microbial mats were isolated by cultivation methods and identified as being of the genera Rhodobacter and Rhodopseudomonas by studying 16S rRNA and pufM gene sequence information. Experiments of oxygen uptake with lower fatty acids revealed that the freshly collected microbial mats and the Rhodopseudomonas isolates had a wider spectrum of carbon utilization and a higher affinity for acetate than did the Rhodobacter isolates. These results demonstrate that the microbial mats were dominated by the purple nonsulfur bacteria of the genera Rhodobacter and Rhodopseudomonas, and the bioavailability of lower fatty acids in wastewater is a key factor allowing the formation of visible microbial mats with these phototrophs.

Optimization of wastewater feeding for single-cell protein production in an anaerobic wastewater treatment process utilizing purple non-sulfur bacteria in mixed culture condition

Impacts of operation timing of feeding and withdrawal on anaerobic wastewater treatment utilizing purple non-sulfur bacteria have been investigated in mixed culture condition with acidogenic bacteria. Simulated wastewater containing glucose was treated in a laboratory-scale chemostat reactor, changing the timing of wastewater feeding and withdrawal. Rhodopseudomonas palustris, which does not utilize glucose as a substrate, was inoculated in the reactor. Rps. palustris was detected by a fluorescent in situ hybridization (FISH) technique using the specific Rpal686 probe. As a result, population ratios of Rps. palustris were over 20% through the operation. Rps. palustris could grow by utilizing metabolites of acidogenic bacteria that coexisted in the reactor. A morning feed was effective for a good growth of purple non-sulfur bacteria. A protein content of cultured bacteria was the highest when wastewater was fed in the morning. Dissolved organic carbon (DOC) removal was 94% independent of the timing control. Consequently, feeding in the morning is the optimum feed-timing control from the aspects of growth of purple non-sulfur bacteria and single-cell protein production.

Applications of photosynthetic bacteria for medical fields

The medical applications of photosynthetic bacteria are summarized. Photosynthetic bacteria can produce various types of physiological active substance such as vitamin B(12), ubiquinone (coenzyme Q10), 5-aminolevulinic acid (ALA), porphyrins and RNA. In particular, photosynthetic bacterial ALA was commercially applied to cancer diagnosis and treatment. Recently, ALA has been applied to the treatment of acne vulgaris and the suppression of the inflammatory response to coronary and iliac injuries. In addition, the recent applications of RNA from a marine photosynthetic bacterium as a medical supplement for immune improvement and suppression of infection are described. Furthermore, the feasible application of a biopolymer consisting of RNA from a photosynthetic bacterium as a drug delivery system (DDS) to cancer treatment is described.

Characterization of a spontaneous nonmagnetic mutant of Magnetospirillum gryphiswaldense reveals a large deletion comprising a putative magnetosome island

Frequent spontaneous loss of the magnetic phenotype was observed in stationary-phase cultures of the magnetotactic bacterium Magnetospirillum gryphiswaldense MSR-1. A nonmagnetic mutant, designated strain MSR-1B, was isolated and characterized. The mutant lacked any structures resembling magnetosome crystals as well as internal membrane vesicles. The growth of strain MSR-1B was impaired under all growth conditions tested, and the uptake and accumulation of iron were drastically reduced under iron-replete conditions. A large chromosomal deletion of approximately 80 kb was identified in strain MSR-1B, which comprised both the entire mamAB and mamDC clusters as well as further putative operons encoding a number of magnetosome-associated proteins. A bacterial artificial chromosome clone partially covering the deleted region was isolated from the genomic library of wild-type M. gryphiswaldense. Sequence analysis of this fragment revealed that all previously identified mam genes were closely linked with genes encoding other magnetosome-associated proteins within less than 35 kb. In addition, this region was remarkably rich in insertion elements and harbored a considerable number of unknown gene families which appeared to be specific for magnetotactic bacteria. Overall, these findings suggest the existence of a putative large magnetosome island in M. gryphiswaldense and other magnetotactic bacteria.

Modeling stability of photoheterotrophic continuous cultures in photobioreactors

Continuous cultures of the purple non-sulfur bacterium Rhodospirillum rubrum were grown in a cylindrical photobioreactor in photoheterotrophic conditions, using acetate as carbon source. A new kinetic and stoichiometric knowledge model was developed, and its ability to simulate experimental results obtained under varying incident light fluxes and residence times is discussed. The model accurately predicts the stable, unstable, or oscillating behavior observed for the reactor productivity. In particular, the values of residence time corresponding to a subcritical bifurcation with a typical hysteresis effect are calculated and analyzed. The robustness of the proposed model allows the engineering operating domain of the photobioreactor function to be set and offers a promising tool for the design and control of such photoheterotrophic processes.

Growth and magnetosome formation by microaerophilic Magnetospirillum strains in an oxygen-controlled fermentor

Media and growth conditions were optimized for the microaerobic cultivation of Magnetospirillum gryphiswaldense in flasks and in a fermentor, resulting in significantly increased cell and magnetosome yields, compared with earlier studies. A reliable method was established for the automatic control of low dissolved oxygen tensions (pO(2)) in the fermentor (oxystat). Growth and magnetosome formation by M. gryphiswaldense, M. magnetotacticum and Magnetospirillum sp. AMB-1 were studied at various oxygen concentrations. Despite differences in their growth responses with respect to oxygen, we found a clear correlation between pO(2) and magnetosome formation in all three Magnetospirillum strains. Magnetite biomineralization was induced only below a threshold value of 20 mbar O(2) and optimum conditions for magnetosome formation were found at a pO(2) of 0.25 mbar (1 bar = 10(5) Pa). A maximum yield of 6.3 mg magnetite l(-1) day(-1) was obtained with M. gryphiswaldense grown under oxystat conditions, which is the highest magnetosome productivity reported so far for a magnetotactic bacterium. In conclusion, the presented results provide the basis for large-scale cultivation of magnetospirilla under defined conditions.

Two-dimensional analysis of proteins specific to the bacterial magnetic particle membrane from Magnetospirillum sp. AMB-1

We report the identification of five proteins expressed specifically on the bacterial magnetic particle (BMP) membrane of Magnetospirillum sp. AMB-1. These proteins are major components of the BMP membrane. The molecular weights were determined to be 12.0, 16.0, 24.8, 35.6, and 66.2 kDa by sodium dodecyl sulfate polyacrylamide gel electrophoresis. Of these five, the 16.0-kDa protein was the most abundant in the BMP membrane. Furthermore, the 16.0-kDa protein consisted of two components each of differing pI. The 35.6-kDa protein was the second most abundant protein of the five detected.

Isolation and characterization of a new denitrifying spirillum capable of anaerobic degradation of phenol

Two kinds of phenol-degrading denitrifying bacteria, Azoarcus sp. strain CC-11 and spiral bacterial strain CC-26, were isolated from the same enrichment culture after 1 and 3 years of incubation, respectively. Both strains required ferrous ions for growth, but strain CC-26 grew better than strain CC-11 grew under iron-limited conditions, which may have resulted in the observed change in the phenol-degrading bacteria during the enrichment process. Strain CC-26 grew on phenol, benzoate, and other aromatic compounds under denitrifying conditions. Phylogenetic analysis of 16S ribosomal DNA sequences revealed that this strain is most closely related to a Magnetospirillum sp., a member of the alpha subclass of the class Proteobacteria, and is the first strain of a denitrifying aromatic compound-degrading bacterium belonging to this group. Unlike previously described Magnetospirillum strains, however, this strain did not exhibit magnetotaxis. It grew on phenol only under denitrifying conditions. Other substrates, such as acetate, supported aerobic growth, and the strain exhibited microaerophilic features.

Formation of magnetosomes in magnetotactic bacteria

The ability of magnetotactic bacteria to orient and migrate along geomagnetic field lines is based on intracellular magnetic structures, the magnetosomes, which comprise nano-sized, membrane bound crystals of magnetic iron minerals. The formation of magnetosomes is achieved by a biological mechanism that controls the accumulation of iron and the biomineralization of magnetic crystals with a characteristic size and morphology within membrane vesicles. This paper focuses on the current knowledge about magnetotactic bacteria and will outline aspects of the physiology and molecular biology of magnetosome formation. The biotechnological potential of the biomineralization process is discussed.

Kinetics of photo-induced electron transfer from high-potential iron-sulfur protein to the photosynthetic reaction center of the purple phototroph Rhodoferax fermentans

The kinetics of photo-induced electrontransfer from high-potential iron-sulfur protein (HiPIP) to the photosynthetic reaction center (RC) of the purple phototroph Rhodoferarfermentans were studied. The rapid photooxidation of heme c-556 belonging to RC is followed, in the presence of HiPIP, by a slower reduction having a second-order rate constant of 4.8 x 10(7) M(-1) x s(-1). The limiting value of kobs at high HiPIP concentration is 95 s(-1). The amplitude of this slow process decreases with increasing HiPIP concentration. The amplitude of a faster phase, observed at 556 and 425 nm and involving heme c-556 reduction, increases proportionately. The rate constant of this fast phase, determined at 425 and 556 nm, is approximately 3 x 10(5) s(-1). This value is not dependent on HiPIP concentration, indicating that it is related to a first-order process. These observations are interpreted as evidence for the formation of a HiPIP-RC complex prior to the excitation flash, having a dissociation constant of -2.5 microM. The fast phase is absent at high ionic strength, indicating that the complex involves mainly electrostatic interactions. The ionic strength dependence of kobs for the slow phase yields a second-order rate constant at infinite ionic strength of 5.4 x 10(6) M(-1) x s(-1) and an electrostatic interaction energy of -2.1 kcal/mol (1 cal = 4.184 J). We conclude that Rhodoferar fermentans HiPIP is a very effective electron donor to the photosynthetic RC.

Shortcut of the photosynthetic electron transfer in a mutant lacking the reaction center-bound cytochrome subunit by gene disruption in a purple bacterium, Rubrivivax gelatinosus

A mutant lacking the reaction center-bound cytochrome subunit was constructed in a purple photosynthetic bacterium, Rubrivivax gelatinosus IL144, by inactivation of the cytochrome gene. Photosynthetic growth of the C244 mutant strain occurred at approximately half the rate of the wild-type strain. Although mutagenesis resulted in a greatly reduced amount of membrane-bound cytochromes c, illumination induced cyclic electron transfer and the generation of membrane potential in the mutant as observed in the wild-type strain. These findings are consistent with previous observations that the cytochrome subunit is absent in the reaction center complex in some species of purple bacteria and that the biochemical removal of the subunit did not significantly affect the in vitro electron transfer from the soluble cytochrome c to the photosynthetic reaction center. These results suggest that the cytochrome subunit in purple bacteria is not essential for photosynthetic electron transfer and growth, even in those species generally containing the subunit.

HiPiP oxido-reductase activity in membranes from aerobically grown cells of the facultative phototroph Rhodoferax fermentans

The role of the periplasmically located, water-soluble, HiPIP (high-potential iron-sulfur protein) in the respiratory chain of the facultative phototroph Rhodoferax fermentans has been examined. The oxidized HiPIP is reduced by succinate-dependent respiration via the bc1 complex, this reaction being inhibited by myxothiazol and/or stigmatellin. The reduced HiPIP can be oxidized by the membrane-bound cytochrome oxidase, this reaction being inhibited by 0.1 mM cyanide. We conclude that aerobically grown Rf. fermentans contains a redox chain in which HiPIP mediates electron transfer between the bc1 complex and the cb-type cytochrome oxidase.

Growth of bacteria with dimorphic vegetative cell cycles

A mathematical model of the growth of bacteria with dimorphic cell cycles is described. In these bacteria motile swarmer cells differentiate to stalked reproductive cells and the proportions of these cell types change in a characteristic fashion during growth. The selection of parameters to fit the model to experimental data can result in the elucidation of the factors controlling the differentiation of swarmer cells.

Nitrogen fixation and nitrogenase activities in members of the family Rhodospirillaceae

Strains of all 18 species of the family Rhodospirillaceae (nonsulfur photosynthetic bacteria) were studied for their comparative nitrogen-fixing abilities. All species, with the exception of Rhodocyclus purpureus, were capable of growth with N2 as the sole nitrogen source under photosynthetic (anaerobic) conditions. Most rapid growth on N2 was observed in strains of Rhodopseudomonas capsulata. Within the genus Rhodopseudomonas, the species R. capsulata, R. sphaeroides, R. viridis, R. gelatinosa, and R. blastica consistently showed the highest in vivo nitrogenase rates (with the acetylene reduction technique); nitrogenase rates in other species of Rhodopseudomonas and in most species of Rhodospirillum were notably lower. Chemotrophic (dark microaerobic) nitrogen fixation occurred in all species with the exception of one strain of Rhodospirillum fulvum; oxygen requirements for dark N2 fixation varied considerably among species and even within strains of the same species. We conclude that the capacity to fix molecular nitrogen is virtually universal among members of the Rhodospirillaceae but that the efficacy of the process varies considerably among species.

Morphogenesis and differentiation in Rhodomicrobium vannielii and other budding and prosthecate bacteria

Images

[Morphological differentiation in non-sulfur purple bacteria]

Cell differentiation in non-sulphur purple bacteria is complicated, as compared to binary fission, during bud formation with production of hyphae and special resting cells of the exospore type, and can be demonstrated in the folowing series of microorganisms: Rhodopseudomonas sulfidophila leads to Rh. capsulata leads to Rh. acidophila leads to Rh. viridis and Rh. palustris leads to Rh. sulfoviridis leads to Rhodom. vannielii. Contrary to phototrophic bacteria multiplying by division, a distinct sequence in appearance of various morphological forms was found in bud-forming bacteria. Formation of specialized cells is regulated by the substrate concentration, accumulation of metabolites, and the population density. Mobile cells are not formed at all or partly, resting cells are formed sometimes at a higher rate, and vegetative cells contain reserve substances in all bud-forming phototrophic bacteria if conditions of the environment are not optimal.

Isolation and growth rates of methanol utilizing Rhodospirillaceae

38 pure culture strains belonging to seven species of the Rhodospirillaceae were isolated from 39 methanol enrichment cultures inoculated with water and mud samples of different habitats. None of the strains exhibited doubling times shorter than 10 h in methanol-bicarbonate media.