Rhodospirillum salinarum sp. nov., a halophilic photosynthetic bacterium isolated from a Portuguese saltern

A new species of halophilic photosynthetic bacteria, Rhodospirillum salinarum, has been isolated and described. Its natural habitat are the terminal crystallization ponds of solar salt production plants. R. salinarum grows optimally at 42°C in the presence of 6–18% NaCl (w/v). Growth requirements are complex, yeast extract and peptone being required both for aerobic heterotrophic and for anaerobic phototrophic growth. Increasing concentrations of NaCl in the growth media did not give rise to any corresponding increase in intracellular concentrations of K⁺, Na⁺, polyalcohols or amino acids. Malate dehydrogenase from R. salinarum is not halophilic, being inhibited even at low concentrations of Na⁺ or K⁺. The GC mol % of DNA from R. salinarum is markedly higher than that for DNA from R. salexigens, the only previously described halophilic species of the genus Rhodospirillum.     

Ectothiorhodospira vacuolata sp. nov., a new phototrophic bacterium from soda lakes

A new phototrophic bacterium was isolated from Jordanian and Kenyan alkaline salt lakes. Cells are rod shaped, 1.5 m wide and 2–4 m long, and motile by polar flagella. They divide by binary fission, and possess photosynthetic membranes as lamellar stacks similar to those in the other species of the genus Ectothiorhodospira and the brown colored Rhodospirillum species. The presence of bacteriochlorophyll a and carotenoids of the normal spirilloxanthin series is indicated by the absorption spectra of living cells. Under certain growth conditions the cells form gas vacuoles, may become immotile and float to the top of the culture medium. Sulfide and thiosulfate are used as photosynthetic electron donors. During the oxidation of sulfide to sulfate, elemental sulfur is formed, which is accumulated outside the cells. The organisms are strictly anaerobic, do not require vitamins, are moderately halophilic and need alkaline pH-values for growth. The new species Ectothiorhodospira vacuolata is proposed.     

A First Record of Obligate Halophilic Aspergilli from the Dead Sea

The isolation of obligate halophilic aspergilli from the Dead Sea and the range of salt tolerance of halophilic fungi isolated, are reported here for the first time. The mycobiota of the Dead Sea isolated in this study, was dominated by Aspergillus and Penicillium species; Cladosporium were found in lesser numbers. All three genera were obtained from the water sample; however, Aspergillus was the only genus obtained from the sediment. There was significant difference in growth of each isolate at different salt concentrations and intraspecies analysis revealed dissimilarity in response of strains to different salt concentrations in the growth medium The isolates were euryhaline, with halotolerance up to 20–25% solar salt, Aspergillus and Penicillium species showing a higher level of halotolerance, as compared to that of Cladosporium. Halophilic fungi were found in greater numbers in the sediment sample as compared to that in the water sample. Penicillium and Cladosporium species were exclusively facultative halophiles, while some species of Aspergillus were facultative halophiles. All the obligate halophiles isolated, belonged to the genus Aspergillus and were identified as A. penicillioides and A unguis, the latter being a first record of the species from the Dead Sea.     

Evidence for adenylylation/deadenylylation control of the glutamine synthetases of Rhodospirillum tenue and Rhodocyclus purpureus

The phylogenetically related phototrophic bacteria Rhodospirillum tenue and Rhodocyclus purpureus modulate activity of their glutamine synthetases by adenylylation/deadenylylation. Evidence for covalent modification includes the inhibitory effect of Mg²⁺ on the activity of glutamine synthetase extracted from cells of either species grown on excess ammonia, and the lack of Mg²⁺ inhibition of activity of the enzyme isolated from N₂-(R. tenue) or glutamine (R. purpureus)-grown cells. In addition, snake venom phosphodiesterase treatment of glutamine synthetase from either species grown on excess ammonia relieved Mg²⁺ inhibition of the enzyme (as measured via the -glutamyl transferase assay), and changed the cation specificity from Mn²⁺ to Mg²⁺ (in the biosynthetic assay).     

Halobacterium volcanii spec. nov., a Dead Sea halobacterium with a moderate salt requirement

A halophilic bacterium was isolated from bottom sediment from the Dead Sea. The organism possessed the properties of the halobacteria, but differed from the known species in two important respects, 1) the cells were disc-shaped and often cupped when grown under optimum conditions, 2) the optimum requirements for sodium chloride was in the range 1.7–2.5 molar which is about half of that generally reported for the halobacteria. The organism was assigned to the genus Halobacterium and described as Halobacterium volcanii spec.nov. The optimum sodium chloride concentration for growth was close to that found in the Dead Sea. The tolerance for magnesium chloride was very high; the organism grew well in media containing magnesium chloride in the concentrations found in the Dead Sea. Halobacterium volcanii is therefore remarkably well fitted for life in the Dead Sea.     

The microbiology and biogeochemistry of the Dead Sea

The Dead Sea is a hypersaline water body. Its total dissolved salts content is on the average 322.6 gm/liter. The dominant cation is Mg (40.7 gm/liter), followed by Na (39.2 gm/liter), Ca (17 gm/liter) and K (7 gm/liter). The major anion is Cl (212 gm/liter), followed by Br (5 gm/liter); SO₄ and HCO₃, are very minor. The lake contains a limited variety of microorganisms and no higher organisms. The number of recorded species is very low, but the total biomass is reasonably high (about 10⁵ bacteria/ml and 10⁴ algal cells/ml). The indigenous flora is comprised mainly of obligate halophylic bacteria, such as the pink, pleomorphicHalobacterium sp., aSarcina-like coccus, and the facultative halophilic green alga,Dunaliella. Sulfate reducers can be isolated from bottom sediments. Recently a unique obligate magnesiophile bacteria was isolated from Dead Sea sediment. Several of the Dead Sea organisms possess unusual properties. TheHalobacterium sp. has extremely high intercellular K⁺ concentration (up to 4.8M) and extraordinary specificity for K⁺ over Na. TheDunaliella has very high intracellular concentration of glycerol (up to 2.1M). The microorganisms exert marked influence on some biogeochemical processes occurring in the lake, such as the control of the sulfur cycle and the formation and diagenesis of organic matter in the sediments. The Dead Sea is an excellent example of the development of two different mechanisms for adjusting to a hostile environment. The algae adjust to the high salinity by developing a mechanism for the exclusion of salts from the intracellular fluid and using glycerol for osmotic regulation. On the other hand, the bacteria adapt to the environment by adjusting their internal inorganic ionic strength, but not composition, to that of the medium. The problem of population dynamics and limiting factors for algal and bacterial productivity are discussed in view of the total absence of zooplankton and other consumers other than bacteria.     

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.     

Bacteriochlorophyll-protein complexes of aerobic bacteria,Erythrobacter longus and Erythrobacter species OCh 114

Bacteriochlorophyll(Bchl)-protein complexes were isolated from obligate aerobic bacteria, Erythrobacter longus and Erythrobacter species OCh 114. The apparent molecular weights, absorption spectra and polypeptide compositions of the light-harvesting complexes were, in general, similar to those of the light-harvesting Bchl-protein complexes of purple photosynthetic bacteria. The reaction center complexes of these bacteria also showed similar properties to those of the purple bacteria except for slightly altered polypeptides. However, the following characteristic features of the light-harvesting systems were found in these aerobic bacteria. Major carotenoids were not bound to the Bchl-protein complex in E. longus. In Erythrobacter sp. OCh 114, a new type of Bchl-protein complex which showed a single absorption band in the near infrared region at 806 nm was obtained. The reaction center of strain OCh 114 was associated with a c-type cytochrome.Abbreviations Bchl bacteriochlorophyll a - RC reaction center - SDS sodium dodecylsulfate - PAGE polyacrylamide gel electrophoresis     

Halobacterium volcanii spec. nov., a Dead Sea halobacterium with a moderate salt requirement.

A halophilic bacterium was isolated from bottom sediment from the Dead Sea. The organism possessed the properties of the halobacteria, but differed from the known species in two important respects, 1) the cells were disc shaped and often cupped when grown under optimum conditions, 2) the optimum requirements for sodium chloride was in the range 1.7--2.5 molar which is about half of that generally reported for the halobacteria. The organism was assigned to the genus Halobacterium and described as Halobacterium volcanni spec. rov. The optimum sodium chloride concentration for growth was close to that found in the Dead Sea. The tolerance for magnesium chloride was very high; the organism grew well in media containing magnesium chloride in the concentrations found in the Dead Sea. Halobacterium volcanii is therefore remarkably well fitted for life in the Dead Sea.     

Haloarcula marismortui (Volcani) sp. nov., nom. rev., an extremely halophilic bacterium from the Dead Sea

An extremely halophilic red archaebacterium isolated from the Dead Sea (Ginzburg et al., J. Gen. Physiol. 55: 187-207, 1970) belongs to the genus Haloarcula and differs sufficiently from the previously described species of the genus to be designated a new species; we propose the name Haloarcula marismortui (Volcani) sp. nov., nom. rev. because of the close resemblance of this organism to "Halobacterium marismortui," which was first described by Volcani in 1940. The type strain is strain ATCC 43049.     

ATP-linked citrate lyase activity in the green sulfur bacterium Chlorobium limicola forma thiosulfatophilum

Cell-free extracts of the green sulfur bacterium Chlorobium limicola forma thiosulfatophilum strains 1C and L have been shown to cleave citrate with the formation of oxaloacetate and acetyl-CoA. This capacity was found in autotrophically grown cells as well as in the cells grown on media with acetate or L-glutamate. Citrate lyase activity in cell-free extracts is only measurable in the presence of citrate, adenosine-5-triphosphate, coenzyme A and Mg²⁺ or Mn²⁺. It is concluded on the basis of the obtained data that C. limicola f. thiosulfatophilum contains adenosine-5-triphosphate-linked citrate lyase (E.C.4.1.3.8). In contrast to green bacteria in the purple bacteria Ectothiorhodospira shaposhnikovii, Rhodospirillum rubrum and Thiocapsa roseopersicina citrate lyase activity was not found.     

Bacteriorhodopsin in a bloom of halobacteria in the Dead Sea

A dense bloom of red halobacteria developed in the Dead Sea in the summer 1980, bacterial densities of up to 1.9 x10⁷ cells ml^-1 were observed. The population consisted of two types: pleomorphic, cup-shaped cells and rod-shaped cells. A high content of bacteriorhodopsin was found in the bloom (up to 0.4 nmol per mg protein). The rod-shaped Halobacterium was isolated and was shown to contain bacteriorhodopsin.Abbreviations 20 specific gravity at 20°C - Tris Tris-(hydroxymethyl)-aminomethane     

Dynamics of a bloom of halophilic archaea in the Dead Sea

After a period of more than ten years in which bacterial and algal community sizes were extremely small, a dense bloom of halophilic archaea developed in the upper 5–10 m of the Dead Sea water column in the summer of 1992. The development of this bloom followed a dilution of the upper water layer by winter rainfloods, which enabled the development of a short-lived dense bloom of the unicellular green alga Dunaliella parva. The dense archaeal community (up to 3.5 × 10⁷ cells m1^–1 in June 1992) imparted a red coloration to the Dead Sea, due to its high content of bacterioruberin. Bacteriorhodopsin was not detected. High levels of potential heterotrophic activity were associated with the bloom, as measured by the incorporation of labeled organic substrates. After the decline of the algal bloom, archaeal numbers in the lake decreased only little, and most of the community was still present at the end of 1993. The amount of carotenoid pigment per cell, however, decreased 2–3-fold between June 1992 and August 1993. No new algal and archaeal blooms developed after the winter floods of 1992–1993, in spite of the fact that salinity values in the surface layer were sufficiently low to support a new algal bloom. A remnant of the 1992 Dunaliella bloom maintained itself at the lower end of the pycnocline at depths between 7 and 13 m (September 1992–August 1993). Its photosynthetic activity was small, and very little stimulation of archaeal growth and activity was associated with this algal community.     

The divalent cation requirement of Dead Sea halobacteria

Pleomorphic Halobacterium strains isolated from the Dead Sea (H. volcanii, H. marismortui) require high concentrations of divalent cations (75 mM Mg²⁺) for growth. When suspended in medium containing less than 50 mM Mg²⁺ cells lose their native shape within minutes and become spherical. This occurs even at elevated sodium chloride concentrations. Concomitant with the morphological changes, a high mlecular weight component which is positive in Coomassie Brilliant Blue and in periodate Schiff stain is released into the surrounding medium. At divalent cation concentrations lower than 100 mM magnesium cells were shown to lose their viability and their ability to incorporate amino acids. The potency of different divalent cations or their combinations to enable growth and stabilize morphology and viability was studied. It is suggested that different mechanisms underlie the divalent cation requirement of the different functions.     

Field and Laboratory Studies on some Photosynthetic Bacteria in Aswan High Dam Lake. II. Isolation and Identification of Purple Non-sulfur Bacteria (Rhodospirillaceae)

485 isolates were recorded from different localities between summer 1984 and spring 1985. These isolates comprise five different genera with eight different species of purple non-sulfur bacteria- Rhodopseudomonas was the most common genus at all sites and was represented by three species. R. acidophila, R. blastica, R. palustris. Rhodomicrobium was the second in frequency and was represented by R. vannielli only. This species was only recorded for khor sites. Rhodocyclus was represented by two species, R. gelatinosus and R. tenuis. Rhodobacter and Rhodospirillum were represented by one species each, Rhodobacter capsulatus and Rhodospirillum rubrum. Khor sites were richer in number of isolates and genera of purple non-sulphur bacteria than the main body of AHDL. Some species were more common in winter and spring while others predominate in summer and autumn.     

The respiratory chain of the halophilic anoxygenic purple bacterium Rhodospirillum sodomense

The halophilic purple nonsulfur bacterium Rhodospirillum sodomense has been previously described as an obligate phototroph that requires yeast extract and a limited number of organic compounds for photoheterotrophic growth. In this work, we report on chemoheterotrophic growth of R. sodomense in media containing either acetate or succinate supplemented with 0.3–0.5% yeast extract. Plasma membranes isolated from cells grown aerobically in the dark contained three b-type and three c-type membrane-bound cytochromes with E _m,7 of +171 ± 10, +62 ± 10 and –45 ± 13 mV (561–575 nm), and +268 ± 6, +137 ± 10 and –43 ± 12 mV (551–540 nm). A small amount of a soluble c-type cytochrome with a mol. mass of 15 kDa (E _m,7≥ +150 mV) was identified. Spectroscopic and immunological methods excluded the presence of cytochrome of the c ₂ class and high-potential iron-sulfur proteins. Inhibitory studies indicated that only 60–70% of the respiratory activity was blocked by low concentrations of cyanide, antimycin A, and myxothiazol (10, 0.1, and 0.2 μM, respectively). These results were interpreted to show that the oxidative electron transport chain of R. sodomense is branched, leads to a quinol oxidase that is fully blocked by 1 mM cyanide and that is involved in light-dependent oxygen reduction, and leads to a cytochrome c oxidase that is inhibited by 10 μM cyanide. These features taken together suggest that R. sodomense differs from the closely related species Rhodospirillum salinarum and from other species of the genus Rhodospirillum in that it contains multiple membrane-bound cytochromes c. Received: 8 June 1998 / Accepted: 25 August 1998     

Some observations on the culture,physiology and morphology of some brown-redRhodospirillum-species

Summary From ditch- and canalwater 21 strains of brown-red, photo-synthetically active spirilla were isolated. These spirilla distinguished themselves fromRhodospirillum rubrum by the composition of their pigment complex and by their behaviour towards oxygen (strictly anaerobic). The strains, judged by morphological characteristics, represented three different species. Two of the species could be identified withRhodospirillum fulvum van Niel resp.Rhodospirillum photometricum Molisch. The third species was found to be a new one, for which the nameRhodospirillum Molischianum was proposed.Regarding the isolation, culture, morphological and physiological characteristics of these organisms detailed data were given. Various organic substances can function as H-donors for these spirilla. The absorption spectra of living cells of the three species show a striking conformity, but there is a distinct difference between the absorption spectra of the brown-redRhodospirillum-species and the absorption spectrum ofRhodospirillum rubrum. The results of a chromatographical analysis of the pigment complex of one of the strains ofRhodospirillum pholometricum make it probable that this difference is due to the absence of the carotenoid spirilloxanthin in the brown-red spirilla.     

Proteolytic modifications of the B800-860 complex of the photosynthetic bacterium Rhodocyclus tenuis: Structural and spectral effects

The modification effects on the absorption and cirular dichroic (CD) spectra of the isolated B800-860 antenna complex of Rhodocyclus tenuis by a number of proteolytic enzymes were investigated. The chymotrypsin modifications of the B800-860 complex led to an about 40% decrease of the 860-nm band and a blue-shift to 841 nm. The biphasic CD signal related to the B860 BChl disappeared and a new double CD signal with a zero-crossing point at 842 nm appeared. These absorption and CD spectral changes suggested that a B800-841 complex resulted after chymotrypsin digestion. The polypeptide components of the chymotrypsin-modified B800-860 complex were separated by reverse-phase chromatography, and their amino acid sequences determined by protein sequencing and mass spectrometry. Sequence analyses showed that the C-terminal 25 residues of the B800-860- polypeptide and the C-terminal 8 residues of the B800-860- polypeptide were cleaved by chymotrypsin, and the remaining , polypeptide fragments apparently form the structural basis for the newly-formed B800-841 complex. No significant spectral change was observed from exposing the isolated B800-860 complex to trypsin, carboxypeptidase A and the combination of carboxypeptidase A and carboxypeptidase B. Short-term proteinase K incubation of the B800-860 complex of Rc. tenuis led to a preferential decrease of the 860-nm absorbance band and its related CD signals, as compared to the 800-nm absorbance and CD bands, suggesting that the C-terminal portions of the antenna polypeptides are possibly exposed to the exterior of the B800-860 complex micelles. Whereas, long-term proteinase K digestion resulted in the spectral collapse of the B800-860 complex and the release of free BChls. Our proteolysis experiments support the hypothesis that the C-terminal portions of the antenna polypeptides play a key role in the redshift and strong molar extinction of the Q_y band of the B850 BChls.Abbreviations B800-860 light-harvesting complex with the absorption maxima (Q_y) at 800 nm and 860 nm - B800-860- -, polypeptide of the B800-860 complex - CD circular dichroism - Deriphat-160 disodium Nlauryl--iminodipropionate - FT Fourier transform - LH light-harvesting - near-IR near infra-red - OG n-Octyl--glucoside - PTH phenylthiohydantoin - Rb. Rhodobacter - Rc. Rhodocyclus - Rp. Rhodopseudomonas - Rsp Rhodospirillum - DSM Deutsche Sammlung für Mikroorganismen     

The size of the photosynthetic unit in purple bacteria

Pigment analysis was performed by means of normal phase HPLC on a number of bacteriochlorophyll a and b containing species of purple bacteria that contain a core antenna only. At least 99% of the bacteriochlorophyll in Rhodobacter sphaeroides R26, Rhodopseudomonas viridis and Thiocapsa pfennigii was esterified with phytol (BChl a _p and BChl b _p, respectively). Rhodospirillum rubrum contained only BChl a esterified with geranyl-geraniol (BChl a _GG). Rhodospirillum sodomense and Rhodopseudomonas marina contained, in addition to BChl a _p, small amounts of BChl a _GG, and presumably also of BChl a esterified with dihydro and tetrahydro geranyl-geraniol (2,10,14-phytatrienol and probably 2,14-phytadienol). In all species bacteriopheophytin (BPhe) esterified with phytol was present. The BChl/BPhe ratio indicated that in these species a constant number of 25 ± 3 antenna BChls is present per reaction centre. This number supports a model in which the core antenna consists of 12 - heterodimers surrounding the reaction centre. Determination of the in vivo extinction coefficient of BChl in the core-reaction centre complex yielded a value of ca. 140 mM^–1 cm^–1 for BChl a containing species and of 130 mM^–1 cm^–1 for Rhodopseudomonas viridis.Abbreviations BChl bacteriochlorophyll - BPhe bacteriopheophytin - GG geranyl-geraniol - LHI and LHII core and peripheral antenna complexes - P phytol - RC reaction centre Dedicated to the memory of Professor D.I. Arnon.     

<Emphasis Type="Italic">Tindallia texcoconensis</Emphasis> sp. nov., a new haloalkaliphilic bacterium isolated from lake Texcoco,Mexico

A new alkaliphilic and moderately halophilic, strictly anaerobic, fermentative bacterium (strain IMP-300^T) was isolated from a groundwater sample in the zone of the former soda lake Texcoco in Mexico. Strain IMP-300^T was Gram-positive, non-sporulated, motile and rod-shaped. It grew within a pH range from 7.5 to 10.5, and an optimum at 9.5. The organism was obligately dependent on the presence of sodium salts. Growth showed an optimum at 35°C with absence of growth above 45°C. It fermented peptone and a few amino acids, preferentially arginine and ornithine, with production of acetate, propionate, and ammonium. Its fatty acid pattern was mainly composed of straight chain saturated, unsaturated, and cyclopropane fatty acids. The G + C content of genomic DNA was 40.0 mol%. Analysis of the 16S rRNA gene sequence indicated that the new isolate belongs to the genus Tindallia, in the low G + C Gram-positive phylum. Phylogenetically, strain IMP-300^T has Tindallia californiensis, as closest relative with a 97.5% similarity level between their 16S rDNA gene sequences, but the DNA–DNA re-association value between the two DNAs was only 42.2%. On the basis of differences in genotypic, phenotypic, and phylogenetic characteristics, strain IMP-300^T is proposed as a new species of the genus Tindallia, T. texcoconensis sp. nov. (type strain IMP-300^T = DSM 18041^T = JCM 13990^T).