Heterotrophic Bacterial Strain Research Articles

Macrocyclic polyketides with siderophore mode of action from marine heterotrophic Shewanella algae: Prospective anti-infective leads attenuate drug-resistant pathogens.

Biotechnological and chemical characterization of previously undescribed homologous siderophore-type macrocyclic polyketides from heterotrophic Shewanella algae Microbial Type Culture Collection (MTCC) 12715 affiliated with Rhodophycean macroalga Hypnea valentiae of marine origin, with significant anti-infective potential against drug-resistant pathogens. The heterotrophic bacterial strain in symbiotic association with intertidal macroalga H. valentiae was isolated to homogeneity in a culture-dependent method and screened for bioactivities by spot-over-lawn assay. The bacterial organic extract was purified and characterized by extensive chromatographic and spectroscopic methods, respectively, and was assessed for antibacterial activities with disc diffusion and microtube dilution methods. The macrocyclic polyketide compounds exhibited wide-spectrum of anti-infective potential against clinically significant vancomycin-resistant Enterococcus faecalis (VREfs), methicillin-resistant Staphylococcus aureus (MRSA), Pseudomonas aeruginosa and Klebsiella pneumonia with minimum inhibitory concentration of about 1-3µgml-1 , insomuch as the antibiotics chloramphenicol and ampicillin were active at ≥6·25µgml-1 . The studied compounds unveiled Fe3+ chelating activity, which designated that their prospective anti-infective activities against the pathogens could be due to their siderophore mechanism of action. In support of that, the bacterium exhibited siderophore production on bioassay involving the cast upon culture agar plate, and the presence of siderophore biosynthetic gene (≈1000bp) (MF 981936) further corroborated the inference. In silico molecular modelling with penicillin-binding protein (PBP2a) coded by mecA genes of MRSA (docking score -11·68 to -12·69kcalmol-1 ) verified their in vitro antibacterial activities. Putative biosynthetic pathway of macrocyclic polyketides through stepwise decarboxylative condensation initiated by malonate-acyl carrier protein further validated their structural and molecular attributes. The studied siderophore-type macrocyclic polyketides from S. algae MTCC 12715 with significant anti-infective potential could be considered as promising candidates for pharmaceutical and biotechnological applications, especially against emerging multidrug-resistant pathogens. This study exhibited the heterotrophic bacteria in association with intertidal macroalga as propitious biological resources to biosynthesize novel antibacterial agents.

Thermaurantimonas aggregans gen. nov., sp. nov., a moderately thermophilic heterotrophic aggregating bacterium isolated from microbial mats at a terrestrial hot spring.

A moderately thermophilic and heterotrophic bacterial strain, LAT, was isolated from microbial mats sampled at a hot spring in Nakabusa, Nagano, Japan. The cells of strain LAT were aerobic, Gram-stain-negative, non-sporulating, non-motile and rod-shaped (2.0-4.1 µm long). The formation of dense cell aggregates in liquid medium was a unique characteristic of the strain. Strain LAT grew optimally at 50°C and at pH 7.5. Phylogenetic analysis based on the 16S rRNA gene sequence revealed that the nearest neighbour of strain LAT was Schleiferia thermophila JCM 30197T with 94.1 % sequence similarity. The draft genome sequence of strain LAT (2 671 880 bp) showed 18.0 % digital DNA-DNA hybridization, 70.9 % average nucleotide identity and 72.1 % average amino acid identity (AAI) values in comparison with the genome sequence of S. thermophila JCM 30197T (2 606 763 bp); the 16S rRNA gene sequence similarity and AAI values are lower than the cutoffs used for assignment to a separate genus. On the basis of phenotypic features, major cellular fatty acid composition, genome sequencing and phylogenetic position, a novel genus and species are proposed for strain LAT, to be named Thermaurantimonas aggregans (= JCM 31826T=DSM 106522T).

Isolation and Characterization of Altererythrobacter sp. DT for Biotreatment of and Sulfur Production from Thiosulfate-Bearing Industrial Wastewater

The objectives of the present study are to isolate thiosulfate-degrading bacterium and optimize its degradative conditions including temperature, pH, and thiosulfate concentrations required for bioremediation purposes. A heterotrophic thiosulfate-degrading bacterial strain DT was successfully isolated from saline soil and identified as Altererythrobacter sp. based on its physicochemical properties and 16S rDNA sequence analysis. It was a naturally occurring methionine auxotrophic strain that utilized only peptone, yeast extract, or several amino acids as the sole carbon source. Altererythrobacter sp. DT degraded thiosulfate via a distinctive disproportionation reaction which was characterized by accumulation of sulfate and elemental sulfur at a molar ratio of 1:1. Optimal conditions for both bacterial growth and thiosulfate metabolism were 25–30 °C and pH 6, respectively. In a fed-batch treatment system receiving liquid polysulfide wastewater, a high degradation rate of 407.3 mg S2O32−/(L h) and an elemental sulfur yield of nearly 50% were achieved for immobilized DT cells, indicating great potential of strain DT for future application in the treatment of and microbial production of elemental sulfur from thiosulfate-bearing industrial wastewater.

Molecular insight into the dynamic central metabolic pathways of Achromobacter xylosoxidans CF-S36 during heterotrophic nitrogen removal processes

Organic carbon sources play a significant role in heterotrophic nitrogen consumption. This quintessential exploration is focused on carbon and nitrogen biogeochemical cycles in heterotrophic bacteria, capable of simultaneous nitrification and denitrification (SND). A heterotrophic bacterial strain Achromobacter xylosoxidans CF-S36 isolated from domestic wastewater efficiently eliminated ammonia, nitrate and nitrite by utilizing different carbon sources. The type of carbon utilized by strain CF-S36 determined the rate of heterotrophic nitrogen removal. Quantitative real-time PCR (qRT-PCR) analysis of genes of central carbon and nitrogen metabolism, signal transduction, electron transport chain (ETC) pathways and assays of enzymes of denitrification processes revealed the existence of well-coordinated link between carbon utilization and nitrogen elimination in bacterial cell. The most preferred carbon source for nitrification was succinate followed by glucose and acetate. Inhibitory effect of nitrite on glycolytic pathway and nitrogen assimilation genes attributes glucose as unfavorable carbon source for denitrification process in strain CF-S36. Acetate served as efficient carbon source for utilizing nitrite through denitrification process. The study demonstrated here might be useful to biogeochemical engineer to understand the involvement of heterotrophic bacteria in global biogeochemical cycle and to gain further insight into the diversified application of these microorganisms.

Bio-alteration of metallurgical wastes by Pseudomonas aeruginosa in a semi flow-through reactor

Metallurgical activities can generate a huge amount of partially vitrified waste products which are either landfilled or recycled. Lead Blast Furnace (LBF) slags are often disposed of in the vicinity of metallurgical plants, and are prone to weathering, releasing potentially toxic chemical components into the local environment. To simulate natural weathering in a slag heap, bioweathering of these LBF slags was studied in the presence of a pure heterotrophic bacterial strain (Pseudomonas aeruginosa) and in a semi-flow through reactor with intermittent leachate renewal. The evolution of water chemistry, slag composition and texture were monitored during the experiments. The cumulative bulk release of dissolved Fe, Si, Ca and Mg doubled in the presence of bacteria, probably due to the release of soluble complexing organic molecules (e.g. siderophores). In addition, bacterial biomass served as the bioadsorbent for Pb, Fe and Zn as 70–80% of Pb and Fe, 40–60% of Zn released are attached to and immobilized by the bacterial biomass.

Wenyingzhuangia marina gen. nov., sp. nov., a member of the family Flavobacteriaceae isolated from a recirculating mariculture system

A Gram-stain-negative, strictly aerobic and heterotrophic bacterial strain, designed strain D1(T), was isolated from a recirculating mariculture system in Tianjin, China. Its taxonomic position was determined using a polyphasic approach. Cells of strain D1(T) were non-flagellated short rods, 0.3-0.5 µm wide and 0.5-1.0 µm long. Growth was observed at 15-30 °C (optimum, 25 °C), at pH 5.5-9.0 (optimum, pH 6.5-7.0) and in the presence of 1-8% (w/v) NaCl (optimum, 2-3 %). Cells contained carotenoid pigments but not flexirubin-type pigments. Strain D1(T) contained MK-6 as the sole menaquinone and phosphatidylethanolamine (PE) as the sole phospholipid and four unidentified lipids. The major cellular fatty acids (>10%) were iso-C15 : 0 (23.2 %), iso-C17 : 0 3-OH (15.2%), C(16 : 1)ω7c/C(16 : 1)ω6c (14.3%), iso-C(15 : 0) 3-OH (13.5%) and iso-C15 : 1 G (10.8%). 16S rRNA gene sequence analyses indicated that strain D1(T) belonged to the family Flavobacteriaceae and showed closest phylogenetic relationship to the genus Lutibacter, with highest sequence similarity to Lutibacter aestuarii MA-My1(T) (92.2%). The DNA G+C content of strain D1(T) was 35.9 mol%. On the basis of phenotypic, chemotaxonomic and phylogenetic data, strain D1(T) was considered to represent a novel species in a new genus of the family Flavobacteriaceae, for which the name Wenyingzhuangia marina gen. nov., sp. nov. is proposed. The type strain of the type species is D1(T) ( = CGMCC 1.12162(T) = JCM 18494(T)).

Temporal variations in the concentrations of bacteria and their lytic phages: an example of an indigenous phage host system in Lake Plußsee, Germany

1. We describe the abundance of an autochthonous alphaproteobacteria Sphingomonas sp. and its lytic phages during a period of about 3 months in Lake Plussee, Northern Germany. This is the first report of a specific autochthonous phage host system of a heterotrophic bacterial strain in a natural freshwater environment. 2. The concentration of bacterial hosts (Sphingomonas sp. strain B18) fluctuated between 20 and 1,150 (median 168) colony-forming units (CFU) mL-1 and the concentration of the specific lytic phages ranged from 20 to 680 (median 110) plaque-forming units (PFU) mL-1. Different Sphingomonas sp. strains were isolated, showing different sensitivity against two phage isolates. The specific virus to bacteria ratio (VBR) varied by a factor of about 280 and ranged from 0.03 to about 8.5 (median 0.6). 3. Encounter rates of 0.0007 to 0.198 d-1 (median 0.03 d-1) were calculated from the measured concentrations of Sphingomonas sp. and its lytic phages. From changes of PFU between two consecutive samplings net phage decay rates in a range between 0.003 and 1.3 d-1 (median 0.26 d-1) were calculated. 4. Concentration factors were calculated which enable sufficient encounter rates to explain the concentrations of bacteria and their phages. 5. The results of Kokjohn et al. (1991) support the suggestion that the explanation of the coexistence of lytic phages and their host bacteria by the used encounter rate model needs to be revised.

Extraction of Copper from Malanjkhand Low-Grade Ore by Bacillus stearothermophilus

Thermophilic bacteria are actively prevalent in hot water springs. Their potential to grow and sustain at higher temperatures makes them exceptional compare to other microorganism. The present study was initiated to isolate, identify and determine the feasibility of extraction of copper using thermophilic heterotrophic bacterial strain. Bacillus stearothermophilus is a thermophilic heterotrophic bacterium isolated from hot water spring, Atri, Orissa, India. This bacterium was adapted to low-grade chalcopyrite ore and its efficiency to solubilize copper from Malanjkhand low-grade ore was determined. The low-grade copper ore contains 0.27% Cu, in which the major copper-bearing mineral is chalcopyrite associated with other minerals present as minor phase. Variation in parameters such as pulp-density and temperatures were studied. After 30days of incubation, it was found that Bacillus stearothermophilus solubilize copper up to 81.25% at pH 6.8 at 60°C.

Arsenite oxidation by a facultative chemolithotrophic bacterium SDB1 isolated from mine tailing

An arsenite (As[III])-oxidizing bacterium, SDB1, was isolated from mine tailing collected from the Sangdong mine area in Korea and showed chemolithotrophic growth on As[III] and CO(2) as the respective electron and carbon sources. SDB1 is Gram-negative, rod-shaped, and belongs to the Sinorhizobium-Ensifer branch of alpha-Proteobacteria. Growth and As[III] oxidation was enhanced significantly by the presence of yeast extract (0.005%) in minimal salt medium containing 5 mM As[III]; decreasing the doubling time from 9.8 to 2.1 h and increasing the As [III] oxidation rate from 0.014 to 0.349 pmol As [III] oxidized cell(-1) h(-1). As[III] oxidation nearly stopped at pH around 4 and should be performed at pH 7 approximately 8 to be most effective. SDB1 was immobilized in calcium-alginate beads and the oxidation capacity was investigated. Specific As[III] oxidation rates obtained with SDB1 (10.1-33.7 mM As[III] oxidized g(-1) dry cell h(-1)) were 10 approximately 16-times higher than those reported previously with a heterotrophic bacterial strain (Simeonova et al., 2005). The stability and reusability of immobilized SDB1 strongly suggested that the immobilized SDB1 cell System can make the As[III] oxidation process technically and economically feasible in practical applications.

Halomonas chromatireducens sp. nov., a new denitrifying facultatively haloalkaliphilic bacterium from solonchak soil capable of aerobic chromate reduction

A heterotrophic bacterial strain AGD 8-3 capable of denitrification under extreme haloalkaline conditions was isolated from soda solonchak soils of the Kulunda steppe (Russia). The strain was classified within the genus Halomonas. According to the results of 16S rRNA gene sequencing, Halomonas axialensis, H. meridiana, and H. aquamarina are most closely related to strain AGD 8-3 (96.6% similarity). Similar to other members of the genus, the strain can grow within a wide range of salinity and pH. The strain was found to be capable of aerobic reduction of chromate and selenite on mineral media at 160 g/l salinity and pH 9.5-10. The relatively low level of phylogenetic similarity and the phenotypic characteristics supported classification of strain AGD 8-3 as a new species Halomonas chromatireducens.

Are bacteria more like plants or animals? Growth rate and resource dependence of bacterial C : N : P stoichiometry

Summary We examined the relative importance of resource composition (carbon : phosphorus molar ratios which varied between 9 and 933) and growth rate (0·5–1·5 h−1) to biomass carbon : nitrogen : phosphorus stoichiometry and nucleic acid content in Escherichia coli grown in chemostats, and in other heterotrophic prokaryotes using published literature. Escherichia coli RNA content and the contribution of RNA‐P to total cellular P increased with increasing growth rate at all supply C : P ratios. Growth rate had a much stronger effect on biomass C : P than did supply C : P, and increased RNA content resulted in low biomass C : P and N : P ratios. However, we observed only twofold variations in biomass C : P and N : P ratios in the experiments, despite a difference of two orders of magnitude in C : P and N : P supply. The response of biomass C : P and N : P ratios to alteration of the supply C : P and N : P ratios revealed that E. coli was strongly homeostatic in its elemental composition. This result, and a literature survey, suggest that each heterotrophic bacterial strain regulates its elemental composition homeostatically within a relatively narrow range of characteristic biomass C : P and N : P ratios. Thus shifts in the dominance of different bacterial strains in the environment are probably responsible for the large variation in bacterial biomass C : P, as has been suggested for crustacean zooplankton. These findings indicate that bacteria are more like animals than plants in terms of biomass C : P and N : P homeostasis.

Thauera mechernichensis sp. nov., an aerobic denitrifier from a leachate treatment plant.

A heterotrophic bacterial strain TL1T capable of aerobic denitrification was previously enriched in continuous culture from a landfill leachate treatment plant and isolated as a pure culture. The taxonomic position of this isolate within the beta-subclass of the Proteobacteria was determined by 16S rDNA sequence analysis and by conventional taxonomy including substrate spectrum, quinone type (ubiquinone Q-8) and cellular fatty acid composition. Detection of the specific polyamine 2-hydroxyputrescine supports the membership of strain TL1T in the beta-subclass of the Proteobacteria. The results of 16S rDNA sequencing showed that the strain clustered with, but was separate from, Thauera aromatica and Thauera selenatis. DNA-DNA hybridization experiments indicated that the new isolate represents a new species of the genus, for which the name Thauera mechernichensis is proposed; the type strain is DSM 12266T.

Effect of variable nutrient supply rates on the RNA level of a heterotrophic bacterial strain

The heterotrophic bacterial strain HIS 53 was grown in a continuous culture under chemostat conditions and at sinusoidal or stepwise variations of the dilution rate; aspartate, ammonium, and phosphate were the growth-limiting nutrients. Within a specific nutrient limitation the growth yield was constant and independent of the applied environmental conditions. Compared with the reference chemostat culture, sinusoidal variations of the dilution rate increased the cellular RNA level by 19%–53% dependent on the growth limitation; stepwise variations caused an increase of the RNA level by 28%–41%. It was hypothesized that under the variable environmental conditions in the natural habitat the physiological potential of the organism is enhanced by some such increase of the cellular RNA level. As a consequence these increased RNA levels influence the competition between heterotrophic bacteria and, as a result, also the composition of the population of heterotrophic bacteria.