l-Aspartate fermentation by a free-livingCampylobacter species

In the fermentation ofl-aspartate by a free-livingCampylobacter spec., the products formed were acetate, succinate, carbon dioxide and ammonia. The oxidative part of the fermentation pathway yielded acetate, succinate, carbon dioxide and ammonia, and the reductive part gave rise to the formation of succinate and ammonia. When grown anaerobically with aspartate, cells contained cytochromesb andc as well as menaquinone. Reduced cytochromeb, but not reduced cytochromec could be reoxidized by fumarate. In the presence of nitrate, 90% of the available electrons were transferred to nitrate, which was reduced to nitrite; the remainder was transported via the fumarate reductase system. Cells grown with aspartate and excess of formate converted aspartate quantitatively to succinate.Abbreviation Used TLC thin layer chromatography     

New motile anaerobic bacteria growing by succinate decarboxylation to propionate

Three strains of new anaerobic, gram-negative bacteria which grew with succinate as sole source of carbon and energy were isolated from anoxic marine and freshwater mud samples. Cells of the three strains were small, non-spore-forming, motile rods or spirilla. The guanine-plus-cytosine content of the DNA of strain US2 was 52.6±1.0 mol%, of strain Ft2 63.5±1.4 mol%, and of strain Ft1 62.6±1.0 mol%. Succinate was fermented stoichiometrically to propionate and carbon dioxide. The growth yields were 1.2–2.6 g dry cell mass per mol succinate degraded. Strains US2 and Ft2 required 0.05% w/v yeast extract in addition to succinate for reproducible growth. Optimal growth occurred at 30°–37°C and pH 6.8–8.0. Addition of acetate as cosubstrate did not stimulate growth with any strain. Strain Ft2 grew only under strictly anaerobic conditions, whereas strains US2 and Ft1 tolerated oxygen up to 20% in the headspace. Strains US2 and Ft2 grew only with succinate. Strain Ft1 also converted fumarate, aspartate, and sugars to propionate and acetate. This strain also oxidized propionate with nitrate to acetate. Very low amounts of a c-type cytochrome were detected in propionate plus nitrate- or glucose-grown cells of this strain (0.4 g x g protein^-1). Moderate activities of avidin-sensitive methylmalonyl-CoA decarboxylase were found in cell-free extracts of all strains.     

Chemotactic behavior of Campylobacter fetus subspecies towards cervical mucus,bovine placenta and selected substances and ion

The chemotaxis of C. fetus subsp. venerealis and C. fetus subsp. fetus was determined in the presence of bovine cervical mucus and bovine placental extract. Some reported substances and ion in those materials, such amino acids, ferrous iron, hormones, sugars and organic acids were also investigated. Bovine cervical mucus, bovine placenta extracts and some substances and ion of these materials namely L–fucose, L– aspartate, L–glutamate, L–serine, ferrous iron, fumarate, pyruvate and succinate were chemoattractants. The chemottraction was significantly larger in higher concentrations of the tested substances and ion and significant differences among tested strains were also observed. Meso-erythritol and hormones bovine placental lactogen, 17β-estradiol, and progesterone did not elicit chemotactical response. In conclusion, this chemotactic behavior may guide the C. fetus navigation in the bovine host''s genital tract and be an important cofactor of tissue tropism for this bacterium.     

Identification of catalase-producingCampylobacter species based on biochemical characteristics and on cellular fatty acid composition

A total of 50 catalase-positive campylobacters from human and animal sources were studied. The nomenclatural type strains ofCampylobacter coli, C. jejuni, C. fetus, andC. fetus subsp.venerealis, a typical strain of the nalidixic acid-resistant thermophilic group, and various clinical isolates were characterized by bacteriological tests and by gas-liquid chromatographic analysis of their cellular fatty acids. The tests most useful in the differentiation of the various catalase-positive species were growth at 25 and 42°C, H₂S production, tolerance to nalidixic acid and to 2,3,5-triphenyltetrazolium chloride, and hippurate hydrolysis. The latter test was the only reliable means to differentiate betweenC. coli andC. jejuni. Differences between.C. fetus andC. jejuni/coli were confirmed by cellular fatty acid compositions. The bacteriological results indicated thatC. fetus andC. jejuni were distinct species, although within the thermophilic campylobacters there were several related taxa that included bothC. coli andC. jejuni strains with typicalC. coli and some thermophilic strains ofC. fetus subsp.fetus at the extremes.     

Genomic analysis of Campylobacter fetus subspecies: identification of candidate virulence determinants and diagnostic assay targets

Background  

Campylobacter fetus subspecies venerealis is the causative agent of bovine genital campylobacteriosis, asymptomatic in bulls the disease is spread to female cattle causing extensive reproductive loss. The microbiological and molecular differentiation of C. fetus subsp. venerealis from C. fetus subsp. fetus is extremely difficult. This study describes the analysis of the available C. fetus subsp. venerealis AZUL-94 strain genome (~75–80%) to identify elements exclusively found in C. fetus subsp. venerealis strains as potential diagnostic targets and the characterisation of subspecies virulence genes.     

A Genomic Island Defines Subspecies-Specific Virulence Features of the Host-Adapted Pathogen Campylobacter fetus subsp. venerealis

The pathogen Campylobacter fetus comprises two subspecies, C. fetus subsp. fetus and C. fetus subsp. venerealis. Although these taxa are highly related on the genome level, they are adapted to distinct hosts and tissues. C. fetus subsp. fetus infects a diversity of hosts, including humans, and colonizes the gastrointestinal tract. In contrast, C. fetus subsp. venerealis is largely restricted to the bovine genital tract, causing epidemic abortion in these animals. In light of their close genetic relatedness, the specific niche preferences make the C. fetus subspecies an ideal model system to investigate the molecular basis of host adaptation. In this study, a subtractive-hybridization approach was applied to the genomes of the subspecies to identify different genes potentially underlying this specificity. The comparison revealed a genomic island uniquely present in C. fetus subsp. venerealis that harbors several genes indicative of horizontal transfer and that encodes the core components necessary for bacterial type IV secretion. Macromolecular transporters of this type deliver effector molecules to host cells, thereby contributing to virulence in various pathogens. Mutational inactivation of the putative secretion system confirmed its involvement in the pathogenicity of C. fetus subsp. venerealis.Campylobacter species are Gram-negative epsilonproteobacteria highly adapted to mucosal surfaces. The majority are human and/or animal pathogens (19, 61). The 18 species comprising the genus Campylobacter display a high degree of host and tissue specificity, which makes them excellent models to study host-pathogen relationships (25). The most prominent member, Campylobacter jejuni, is a commensal of the chicken intestine and the major cause of human bacterial diarrhea (74). Comparative analysis of Campylobacter genomes has revealed a process of genome decay—supported by a small genome size (about 1.5 Mb) and the loss of metabolic genes—consistent with successful adaptation to a specific niche (41). Campylobacter genomes are among the densest bacterial genomes known, with about 95% coding sequence. Despite this evidence of reduction, plasticity in genetic composition remains evident, as strain-specific genes comprise a substantial proportion of the entire repertoire of 1,500 to 1,800 genes (16, 23, 25, 56).This study focuses on the species Campylobacter fetus, which is represented by the two subspecies C. fetus subsp. fetus and C. fetus subsp. venerealis. Although the two taxa are genetically closely related, they exhibit striking tissue and host specificity. C. fetus subsp. fetus is a human, as well as animal, pathogen. Human infection results in serious systemic disease, especially in immunocompromised people. C. fetus subsp. fetus is the Campylobacter species most often isolated from human blood (75), and it is considered an emerging pathogen (9). The infection mode shares similarities with that of Salmonella enterica serovar Typhi. Orally acquired C. fetus subsp. fetus penetrates the intestinal mucosa, leading to bacteremia, and subsequent excretion via the biliary tract leads to secondary colonization of the intestine (9). Colonization of reproductive organs induces abortion in sheep and to a lesser extent in cattle, and very rarely in humans (11). C. fetus subsp. fetus can also be isolated from the intestinal tracts of birds and reptiles (78, 80). In contrast, C. fetus subsp. venerealis is host restricted. It is isolated primarily from the bovine genital tract and causes the epidemic disease bovine venereal campylobacteriosis (BVC). The reservoir of C. fetus subsp. venerealis is the penile prepuce of the bull. Transmission to cows occurs at coitus or during artificial insemination, and infection leads to endometritis, abortion, and infertility (28). Since BVC is a worldwide problem with substantial economic consequences, diagnosed cases must be registered (75) and import and export of bovine semen and embryos for cattle breeding requires statutory preclusion of C. fetus infection (2). Despite the distinct niche preferences of the C. fetus subspecies, they show high genetic relatedness, complicating the task of correct subspecies identification (46, 62, 81). Their population structure is clonal, and C. fetus subsp. venerealis is thought to represent a bovine clone of C. fetus (81).In this study, we employed the C. fetus subspecies to investigate the genetic basis for their host and tissue specificities. A genomic subtractive-hybridization approach was taken to identify subspecies-specific genomic fragments. This led to the discovery of a genomic island exclusively present on the chromosome of the host-adapted subspecies C. fetus subsp. venerealis. This island harbors a type IV secretion system (T4SS), as well as mobility genes (insertion sequence [IS] transposases and phage integrases) and shares substantial homology and similar structure with resistance plasmids found in other Campylobacter species. These features are indicative of a horizontally acquired genetic element. Finally, mutational analysis of genes within the island substantiates its involvement in C. fetus subsp. venerealis virulence.     

Utilization of hydrogen and formate by Campylobacter spec. under aerobic and anaerobic conditions

A free-living aspartate-fermenting Campylobacter spec. was shown to utilize hydrogen produced in mixed culture by Clostridium cochlearium from glutamate. Resting cells of Campylobacter were shown to reduce aspartate, fumarate and malate as well as nitrate, nitrite, hydroxylamine, sulphite, thiosulphate and elemental sulphur with molecular hydrogen. Growth of Campylobacter spec. was demonstrated with formate as electron donor and nitrate, thiosulphate, elemental sulphur or oxygen as electron acceptor in the presence of acetate as carbon source.     

Aerobic and anaerobic metabolism of Listeria monocytogenes in defined glucose medium.

A defined medium with glucose as the carbon source was used to quantitatively determine the metabolic end products produced by Listeria monocytogenes under aerobic and anaerobic conditions. Of 10 strains tested, all produced acetoin under aerobic conditions but not anaerobic conditions. Percent carbon recoveries of end products, typified by strain F5069, were as follows: lactate, 28%; acetate, 23%; and acetoin, 26% for aerobic growth and lactate, 79%; acetate, 2%; formate, 5.4%; ethanol, 7.8%; and carbon dioxide, 2.3% for anaerobic growth. No attempt to determine carbon dioxide under aerobic growth conditions was made. The possibility of using acetoin production to assay for growth of L. monocytogenes under defined conditions should be considered.     

Morphological Differences in Flagella in Campylobacter fetus Subsp. intestinalis and C. fetus Subsp. jejuni

Intact flagella were isolated from human pathogenic strains of Campylobacter, C. fetus subsp. intestinalis and C. fetus subsp. jejuni, by the method of DePamphilis and Adler and examined by electron microscopy. The isolated flagella were composed of a filament, a hook, a basal body, and a large disk associated with the end of the hook region covering the basal body. The width of the hook was approximately 28 nm, somewhat greater than that of the filament (20 nm in diameter). The hook region of C. fetus subsp. intestinalis was curved, but it was straight in C. fetus subsp. jejuni. The structure of the basal body of the two subspecies was similar to that reported for other gram-negative bacteria. The large disk detached from the flagella showed concentrically arranged circular structures. This structure was more clearly observed in the disk of C. fetus subsp. jejuni than in C. fetus subsp. intestinalis. Observations of thin-sectioned profiles at the attachment site of the flagellum revealed that the large disk is located on the inner side of the outer membrane. The role of the large disk in bacterial movement is not clear, but it is assumed that it acts as an organ to protect the flagellar insertion site from vigorous rotation of the polar end inflicted during bacterial movement.     

Induction of competence in nonencapsulated and encapsulated strains ofHaemophilus influenzae

A simple procedure for induction of competence in nonencapsulated and encapsulated strains ofHaemophilus influenzae is described, which consists of growing cells without shaking in brain-heart infusion broth under aerobic conditions. Competence emerged at the end of the exponential phase and reached a peak at the stationary phase. InH. influenzae Rd competence was maintained for at least 6 h at 37°C, whereas in two encapsulated clinical isolates ofH. influenzae type b a decrease in competence was observed after 4 h. Competence was maintained for 24 h at 22°C and 4°C as well as by freezing the cells in 15% glycerol and storing them at –70°C. Transformation frequencies of three chromosomal markers—streptomycin, nalidixic acid, and erythromycin resistance—were 0.5% to 1% inH. influenzae Rd and about tenfold lower in the two encapsulated clinical isolates ofH. influenzae type b. The advantage of this procedure is that it is simpler than the previously described procedures and yields stable, highly transformable cells. Unlike the standard M IV method, the static aerobic procedure does not interfere with the capsule synthesis and can be used for testing transforming activity of encapsulated virulent isolates ofH. influenzae.     

Studies on decomposition ofCeratophyllum demersum litter under laboratory and field conditions: losses of dry mass and nutrients,qualitative changes in organic compounds and consequences for ambient water and sediments

A study was made of decomposition ofCeratophyllum demersum litter over a 17-day period under controlled conditions of temperature and oxygen (5, 10 and 18 °C; aerobic and anaerobic) and over a 169-day period in the field (Lake Vechten, The Netherlands). Litter, water and sediment were sampled on the 0, 2, 4, 7 and 17th day under controlled conditions and on the 0, 17, 49, 127 and 169th day in the field. The litter was analyzed quantitatively for dry mass, ash, carbon, nitrogen, phosphorus and qualitatively of organic composition by pyrolysis mass spectrometry. The water was analyzed for the elemental concentrations of organic carbon (total and dissolved), nitrogen (total, ammonia and particulate) and phosphorus (total and orthophosphate) and for the concentrations of photosynthetic pigments and bacteria. The sediment was analyzed for the elemental concentrations of nitrogen, carbon and phosphorus, and for bacterial numbers.The pattern of litter mass loss fitted an exponential model fairly well. Mass decreased faster under controlled aerobic than under anaerobic conditions and the decrease was stimulated by increasing temperature, relatively more in the range of 5 to 10 °C (by 20%) than in the range of 10 of 18 °C (by 2%). The residual mass ranged from 73 to 43% of initial under controlled aerobic conditions and from 84 to 65% under anaerobic conditions after 17 days. It decreased far less in the field, to 38% of initial mass in the field after 169 days.The litter initially lost a carbohydrate fraction by leaching in all treatments. The protein content decreased initially as well but increased subsequently at increasing temperature stimulated under anaerobic conditions. The changes in organic composition were correlated with those in nitrogen but not with those in carbon and phosphorus contents. The organic composition of litter incubated in the field differed from that of litter incubated in the laboratory. The field residues contained less proteinaceous material than the laboratory residues.The changes in carbon, nitrogen and phosphorus concentrations in the litter showed different patterns. The carbon concentration generally increased, the nitrogen concentration initially dropped and increased subsequently, and the phosphorus concentration initially dropped and remained relatively constant subsequently. Chemical immobilization of the decomposition process may have occurred in the laboratory, but was unlikely in the field.Carbon, nitrogen and phosphorus left the litter initially largely in particulate form and were recovered in the water. The ratio dissolved: total nutrient concentration was lower under controlled aerobic than under anaerobic conditions. Increasing temperature stimulated bacterial use of dissolved organic carbon and nitrogen. A rapid nutrient flow occurred from macrophyte litter, via water to sediment.The phytoplankton biomass in the water was greatly stimulated by substances freed from the decomposing litter. Diatoms increased generally relatively more than green algae, predominating alternatively with green algae under aerobic conditions and continuously under anaerobic conditions. Bacterial numbers in the water initially increased, partly due to transgression of bacteria from the sediment-water interface to the water and partly due to an actual increase in community biomass. The bacteria returned largely to the sediment-water interface, stimulated by increasing temperature, as most of the substrate readily usable by them had left the litter in the litter-bag and was associated with the upper sediment layers.It is feasible that the annual die-off of theC. demersum population of Lake Vechten barely affects nutrient cycling in the lake, because the contribution to the nutrient pools of the lake when fully mixed is only small. However, small particles originating from decomposingC. demersum litter may influence the lake considerably by decreasing water transparency and serving as a food source for filter-feeders and detritivorous macrofauna.     

Use of PCR for Direct Detection of Campylobacter Species in Bovine Feces

This study reports on the use of PCR to directly detect and distinguish Campylobacter species in bovine feces without enrichment. Inhibitors present in feces are a major obstacle to using PCR to detect microorganisms. The QIAamp DNA stool minikit was found to be an efficacious extraction method, as determined by the positive amplification of internal control DNA added to bovine feces before extraction. With nested or seminested multiplex PCR, Campylobacter coli, C. fetus, C. hyointestinalis, and C. jejuni were detected in all fecal samples inoculated at ≈10⁴ CFU g⁻¹, and 50 to 83% of the samples inoculated at ≈10³ CFU g⁻¹ were positive. At ≈10² CFU g⁻¹, C. fetus, C. hyointestinalis, and C. jejuni (17 to 50% of the samples) but not C. coli were detected by PCR. From uninoculated bovine feces, a total of 198 arbitrarily selected isolates of Campylobacter were recovered on four commonly used isolation media incubated at three temperatures. The most frequently isolated taxa were C. jejuni (152 isolates) and C. lanienae (42 isolates), but isolates of C. fetus subsp. fetus, Arcobacter butzleri, and A. skirrowii also were recovered (≤2 isolates per taxon). Considerable variability was observed in the frequency of isolation of campylobacters among the four media and three incubation temperatures tested. With genus-specific primers, Campylobacter DNA was detected in 75% of the fecal samples, representing an 8% increase in sensitivity relative to that obtained with microbiological isolation across the four media and three incubation temperatures tested. With nested primers, C. jejuni and C. lanienae were detected in 25 and 67% of the samples, respectively. In no instance was DNA from either C. coli, C. fetus, or C. hyointestinalis detected in uninoculated bovine feces. PCR was more sensitive than isolation on microbiological media for detecting C. lanienae (17%) but not C. jejuni. Campylobacters are a diverse and fastidious group of bacteria, and the development of direct PCR not only will increase the understanding of Campylobacter species diversity and their frequency of occurrence in feces but also will enhance the knowledge of their role in the gastrointestinal tract of livestock and of the factors that influence shedding.     

Development of Experimental Genetic Tools for Campylobacter fetus

Molecular analysis of the virulence mechanisms of the emerging pathogen Campylobacter fetus has been hampered by the lack of genetic tools. We report the development and functional analysis of Escherichia coli-Campylobacter shuttle vectors that are appropriate for C. fetus. Some vectors were constructed based on the known Campylobacter coli plasmid pIP1455 replicon, which confers a wide host range in Campylobacter spp. Versatility in directing gene expression was achieved by introducing a strong C. fetus promoter. The constructions carry features necessary and sufficient to detect the expression of phenotypic markers, including molecular reporter genes in both subspecies of C. fetus, while retaining function in C. jejuni. The capacity to express several gene products from different vectors in a single host can be advantageous but requires distinct plasmid replicons. To this end, replication features derived from a cryptic plasmid of C. fetus subsp. venerealis strain 4111/108, designated pCFV108, were adapted for a compatible series of constructions. The substitution of the C. coli replication elements reduced vector size while apparently limiting the host range to C. fetus. The complementation of a ciprofloxacin-resistant mutant phenotype via vector-driven gyrA expression was verified. Cocultivation demonstrated that shuttle vectors based on the pCFV108 replicon were compatible with pIP1455 replication functions, and the stable maintenance of two plasmids in a C. fetus subsp. venerealis host over several months was observed. The application of both vector types will facilitate the investigation of the genetics and cellular interactions of the emerging pathogen C. fetus.     

Growth Properties of Rhodospirillum rubrum Mutants and Fermentation of Pyruvate in Anaerobic, Dark Conditions

Mutant C and G1 were obtained earlier from Rhodospirillum rubrum S(1) during growth in the dark under strict anaerobic conditions in medium containing sodium pyruvate. Mutant C and mutant G1 grew in the dark with generation times of 5.8 h and 4.6 h, respectively. Mutant C cells grew equally well when switched between anaerobic (dark or light) or aerobic, dark conditions. Mutant G1 cells grew only in the dark (anaerobic or aerobic conditions), but a fraction of cells in anaerobic, dark cultures grew when placed in light. This number increased about 3,000-fold when G1 cells were incubated aerobically in the dark. During anaerobic, dark growth, C and G1 organisms incorporated similar amounts of [2-(14)C]sodium pyruvate. About 34% of the incorporated radioactivity was found in lipid fractions from C cells that developed chromatophores during dark growth. Similar results were obtained using G1 cells, which formed only trace amounts of photosynthetic structures. Both mutants fermented sodium pyruvate and produced acetate, formate, carbon dioxide, and hydrogen gas. Molar growth yield coefficients indicated that the cells obtained about 1 mol of adenosine triphosphate per mol of sodium pyruvate fermented. Results suggested that pyruvate fermentation during dark growth occurred via a pyruvate formate-lyase or the pyruvate ferredoxin-oxidoreductase pathway, or both.     

Anaerobic mineralization of cholesterol by a novel type of denitrifying bacterium

A novel denitrifying bacterium, strain 72Chol, was enriched and isolated under strictly anoxic conditions on cholesterol as sole electron donor and carbon source. Strain 72Chol grew on cholesterol with oxygen or nitrate as electron acceptor. Strictly anaerobic growth in the absence of oxygen was demonstrated using chemically reduced culture media. During anaerobic growth, nitrate was initially reduced to nitrite. At low nitrate concentrations, nitrite was further reduced to nitrogen gas. Ammonia was assimilated. The degradation balance measured in cholesterol-limited cultures and the amounts of carbon dioxide, nitrite, and nitrogen gas formed during the microbial process indicated a complete oxidation of cholesterol to carbon dioxide. A phylogenetic comparison based on total 16S rDNA sequence analysis indicated that the isolated micro-organism, strain 72Chol, belongs to the β2-subgroup in the Proteobacteria and is related to Rhodocyclus, Thauera, and Azoarcus species. Received: 16 July 1996 / Accepted: 5 December 1996     

Carbohydrate catabolism in the plerocercoids of Schistocephalus solidus (Cestoda: Pseudophyllidea)

The plerocercoids of S. solidus possess a complete sequence of glycolytic and tricarboxylic acid cycle enzymes. The presence of phosphoenolpyruvate carboxykinase and fumarate reductase activity and the relatively low activities of aconitase and isocitrate dehydrogenase suggest that carbon dioxide fixation is an important pathway in this parasite. Carbon balances show that glycogen is the main energy source under both aerobic and anaerobic conditions and there is only a slight Pasteur effect. Aerobically 22·5% of the glycogen catabolized is excreted as acetate and propionate (4:1), anaerobically 70% of the glycogen utilized can be accounted for as acetate and propionate (1:3). The results indicate that anaerobically the plerocercoids fix carbon dioxide and have a partial reversed tricarboxylic acid cycle, whilst under aerobic conditions at least part of the carbohydrate may be oxidized via a functional tricarboxylic acid cycle.     

Characterization of thermophilicCampylobacter: I. Carbon-substrate utilization tests

The carbon-substrate utlization profile of 234 wild strains of thermophilic campylobacters originating from different animal sources and different part of the world was studied using a microgallery as well as the profile of 25 type strains ofCampylobacter species and reference strains ofCampylobacter-like organisms. Among the 98 substrates tested, succinate, fumarate,d-l-lactate,l-malate, pyruvate,l-glutamate,l-aspartate, andl-serine (with one exception for the last two) were always utilized by the wild strains, and acetate, propionate,d-malate, 2-cetoglutarate, itaconate, citrate, andl-proline by some of the strains. A strong association was found between assimilation ofd-malate and a positive hippurate test.     

Aspartate in the intestine: dual service as anaerobic electron acceptor and nitrogen source

Fumarate was previously known to serve as an anaerobic electron acceptor by E. coli when colonizing the mammalian intestine, but the source of that fumarate was elusive. In this issue, Unden and coworkers demonstrate that l -aspartic acid is the source of fumarate that drives anaerobic respiration by colonized E. coli (Schubert et al., 2021). Moreover, Schubert et al., establish that E. coli is able to grow anaerobically by using aspartate as a sole source of nitrogen. These groundbreaking findings indicate that a single amino acid – aspartate – supports anaerobic respiration and acquisition of nitrogen by E. coli in the intestine.     

Effect of Cultivation Conditions on the Growth and Activities of Sulfur Metabolism Enzymes and Carboxylases of Sulfobacillus thermosulfidooxidans subsp. asporogenes Strain 41

The moderately thermophilic acidophilic bacterium Sulfobacillus thermosulfidooxidans subsp. asporogenes strain 41 is capable of utilizing sulfides of gold–arsenic concentrate and elemental sulfur as a source of energy. Growth in the presence of S⁰ under auto- or mixotrophic conditions was less stable than in media containing iron monoxide. The enzymes involved in the oxidation of sulfur inorganic compounds—thiosulfate-oxidizing enzyme, tetrathionate hydrolase, rhodanase, adenylyl phosphosulfate reductase, sulfite oxidase, and sulfur oxygenase—were determined in the cells of the sulfobacilli grown in mineral medium containing 0.02% yeast extract and either sulfur or iron monoxide and thiosulfate. Cell-free extracts of the cultures grown in the medium with sulfur under auto- or mixotrophic conditions displayed activity of the key enzyme of the Calvin cycle—ribulose bisphosphate carboxylase—and several other enzymes involved in the heterotrophic fixation of carbon dioxide. Activities of carboxylases depended on the composition of the cultivation media.     

Description ofCampylobacter laridis,a new species comprising the nalidixic acid resistant thermophilicCampylobacter (NARTC) group

Ten strains of the nalidixic acid-resistant thermophilicCampylobacter (NARTC) group, of which 2 were isolated from human feces, were compared with 12 reference strains representing various species ofCampylobacter. The NARTC strains were a homogeneous group with respect to their cell morphology and 28 physiological and biochemical characters. All were microaerophilic, motile (amphitrichate), gram-negative, curved, S-shaped or helical rods, and representative strains had mean DNA base compositions of 31 to 32 mol % G+C. Distinctive features of the 10 strains were resistance to nalidixic acid and anaerobic growth in the presence of trimethylamine N-oxide hydrochloride (TMAO). The latter feature may account for the common occurrence of NARTC strains in the fecal contents of seagulls. DNA-DNA hybridizations indicated high (≥76%) base sequence relatedness within the group and low (≤15%) relatedness to other species ofCampylobacter. The 10 strains were classified in the genusCampylobacter but they could not be assigned to any previously defined species. Therefore, a new species, with the nameCampylobacter laridis, is proposed for these 10 strains; the type strain is NCTC 11352.