Natural Bacterial Consortia Research Articles

Distinct Bacterial Consortia Established in ETBE-Degrading Enrichments from a Polluted Aquifer

Ethyl tert-butyl ether (ETBE) is a gasoline additive that became an important aquifer pollutant. The information about natural bacterial consortia with a capacity for complete ETBE degradation is limited. Here we assess the taxonomical composition of bacterial communities and diversity of the ethB gene (involved in ETBE biodegradation) in ETBE-enrichment cultures that were established from a gasoline-polluted aquifer, either from anoxic ETBE-polluted plume water (PW), or from an upstream non-polluted water (UW). We used a 16S rRNA microarray, and 16S rRNA and ethB gene sequencing. Despite the dissimilar initial chemical conditions and microbial composition, ETBE-degrading consortia were obtained from both PW and UW. The composition of ETBE-enrichment cultures was distinct from their initial water samples, reflecting the importance of the rare biosphere as a reservoir of potential ETBE degraders. No convergence was observed between the enrichment cultures originating from UW and PW, which were dominated by Mesorhizobium and Hydrogenophaga, respectively, indicating that distinct consortia with the same functional properties may be present at one site. Conserved ethB genes were evidenced in both PW and UW ETBE-enrichment cultures and in PW water. Our results suggest that the presence of ethB genes rather than the taxonomical composition of in situ bacterial communities indicate the potential for the ETBE degradation at a given site.

Biodegradation of nodularin and other nonribosomal peptides by the Baltic bacteria

Microcystins (MCs) and nodularin (NOD), the hepatotoxic nonribosomal peptides (NRPs) produced by cyanobacteria, are considered as natural pollutants of many aquatic ecosystems. Removal of the toxins proceeds mainly through biodegradation and/or photolysis. In this study, microbial degradation of NOD and other NRPs produced by Nodularia spumigena was investigated. Both, natural bacterial consortia and individual strains from the Southern Baltic Sea were used. Bacterial samples were also screened for the presence of mlrA-D genes, previously proved to be involved in the enzymatic breakdown of hepatotoxic cyanopeptides. The Baltic sediments, with natural bacterial consortia, showed NOD-degrading activity throughout the whole year. These samples were also active against other NRPs: anabaenopeptins and spumigins. The time required for NOD biodegradation ranged from 3 to 41 days and depended on the NOD content in the collected sediments. NOD-degrading activity was also revealed in the presence of ten bacterial strains isolated from sediments and three strains isolated from filaments of N. spumigena CCNP1401. The mlrA-D genes were not found in sediments and only individual genes from the entire mlr cluster were detected in five isolated bacteria. The results suggest that in the case of Baltic bacteria other genes are involved in the biosynthesis of NOD-degrading enzymes.

Rates of Fe(II)-Oxidation and Solubility of Bacteriogenic Iron Oxides

ABSTRACTThe oxidation of Fe(II) at circumneutral pH by natural bacterial consortia capable of oxidizing Fe(II) in flocculent mats of bacteriogenic iron oxides (BIOS) was investigated in a series of microcosm experiments under constant pH and pO2 conditions. The oxidation of Fe(II) was faster in the presence BIOS compared to chemical oxidation in solution with pseudo–first-order rate constants ranging from 0.036 to 0.248 min−1 for BIOS compared to 0.004 min−1 for the chemical control. The Fe(II)-oxidation rates exhibited a kinetic dependency on BIOS concentrations, measured in terms of a pseudo–second-order rate constant at 0.066 Lg−1min−1. From the asymptotic decline in Fe(total) in the microcosms, apparent rate constants for HFO dissolution (zero-order values 0.001 to 0.046 mgL−1min−1) and precipitation (second-order values 0.007 to .297 min−1) were obtained from the BIOS and control microcosms, which yield an apparent equilibrium BIOS solubility of 0.157 mgL−1 (i.e., 2.8 μM). These results reflect the complex interplay of Fe(II) oxidation reactions associated with BIOS including homogenous chemical oxidation in solution, chemical oxidation on HFO surfaces, and bacterially mediated oxidation. Furthermore, BIOS precipitated in response to Fe(II) oxidation exhibit a greater apparent solubility than more stable varieties of HFO. The implication is that the competitive advantage of Fe(II)-oxidizing bacteria over autocatalytic surface chemical Fe(II) oxidation on HFO might be enhanced by a reduction in the total amount of BIOS that is precipitated.

Cellulosic ethanol production by natural bacterial consortia is enhanced by Pseudoxanthomonas taiwanensis.

BackgroundNatural bacterial consortia are considered a promising solution for one-step production of ethanol from lignocellulose because of their adaptation to a wide range of natural lignocellulosic substrates and their capacity for efficient cellulose degradation. However, their low ethanol conversion efficiency has greatly limited the development and application of natural bacterial consortia.ResultsIn the present study, we analyzed 16 different natural bacterial consortia from a variety of habitats in China and found that the HP consortium exhibited relatively high ethanol production (2.06 g/L ethanol titer from 7 g/L α-cellulose at 55°C in 6 days). Further studies showed that Pseudoxanthomonas taiwanensis played an important role in the high ethanol productivity of HP and that this strain effectively boosted the ethanol production of various other natural bacterial consortia. Finally, we developed a new consortium, termed HPP, by optimizing the proportion of P. taiwanensis in the HP consortium to achieve the highest ethanol production reported for natural consortia. The ethanol conversion ratio reached 78%, with ethanol titers up to 2.5 g/L.ConclusionsIn the present study, we found a natural bacterial consortium with outstanding ethanol production performance, and revealed an efficient method with potentially broad applicability for further improving the ethanol production of natural bacterial consortia.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-014-0186-7) contains supplementary material, which is available to authorized users.

Efecto de la asociación alga-bacteria Bostrychia calliptera (Rhodomelaceae) en el porcentaje de remoción de cromo en laboratorio

The effect of chromium removal by Algae-bacteria Bostrychia calliptera (Rhodomelaceae) consortia under laboratory conditions. Water pollution is one of the most important environmental problems worldwide. Recently, biotechnology studies have oriented efforts to study algae-bacterium consortia with the aim to understand the mechanisms to find a possible solution in environmental sciences. This study determined the percentage of chromium removal by the alga-bacterium association exposed to a set of different chromium concentrations under controlled in vitro conditions. Wild plants of Bostrychia calliptera associated with bacterial populations were collected from Dagua River, Pacific coast of Colombia, and were monitored in the laboratory. The trial was conducted with synthetic seawater in bioreactors at two chromium levels: 5 and 10mg/L, and four different experimental treatments: i) algae-bacteria (AB), ii) algae with antibiotic (AA), iii) algal surface sediment, Natural Bacterial Consortium (CBN), and iv) the control without algae or bacteria. The experimental design followed a model of two factors (chromium concentration x combination types) with repeated measures using one factor. The microbial population behavior and the chromium concentration percentage were monitored by using atomic absorption spectroscopy (AAS). According to the data, Algae-bacteria (AB) treatment was the most efficient combination at 10mg/L (87%), whereas the bacterial consortia (CBN) was the most efficient at 5mg/L (62.85%). The results showed significant differences of chromium uptake between algae-bacteria (AB) and natural bacterial consortia (CBN), meaning the importance of those treatments in the chromium removal from coastal waters.

Bactericidal action of illuminated TiO2 on pure Escherichia coli and natural bacterial consortia: post-irradiation events in the dark and assessment of the effective disinfection time

Bactericidal action of illuminated TiO2 on pure culture of Escherichia coli K12 and bacterial consortium was studied. Photocatalytic E. coli inactivation rate was dependent on the biological parameters such as: physiological state, generation and initial concentration of bacteria. The behavior of the bacterial suspension during the subsequent dark period was discussed in order to estimate the potential of using the photocatalytic treatment process in a real water disinfection situation.The effective disinfection time (EDT) was defined as the time required for total inactivation of bacteria without re-growth in a subsequent dark period referenced at 48h.An increase of E. coli concentration was observed after illumination of bacteria without TiO2 (named here as photolysis). In the presence of TiO2 (photocatalysis), the decrease of bacteria continues in the dark, and no regrowth was observed within the following 60h. The extent of this “residual disinfecting effect” was dependent on the light intensity (400 or 1000W/m2) applied during the illumination period. Thus, EDT was reached in photocatalytic but not in photolytic treatment.Bacterial consortia present in two different wastewaters were phototreated with and without TiO2 and a significant difference in bacterial sensitivity to both phototreatments was observed. Enterococcus sp. appear to be less sensitive than coliforms and other Gram-negative bacteria. Considerable differences in photoreactivity were observed for both samples taken at the same place but at different date.The first sample named as wastewater 1, exhibited a bacteriostatic but no bactericidal effect after both phototreatments; the addition of TiO2 accelerated the solar disinfection. In the second sample, wastewater 2, a bactericidal effect was observed in photolytic and photocatalytic experiments and the EDT was attained in both cases, even if the bacterial inactivation rate was the lowest in the presence of the catalyst. The chemical oxygen demand (COD) decreases during photocatalytic treatment, but not during the photolytic one; whereas the Dissolved organic carbon (DOC) increases in both cases. COD/DOC ratio decreases during phototreatments.

Biodegradation of total petroleum hydrocarbon (TPH) in Jordanian petroleum sludge

Bioremediation, or the use of micro-organisms to decontaminate soil or groundwater, is being increasingly seen as an effective, environment-friendly treatment for oil-contaminated sites. In this study, the results are presented concerning a laboratory screening of several natural bacterial consortia and laboratory tests to establish the performance in degradation of hydrocarbons contained in oily sludge from the Jordan Oil Refinery Plant. As a result of the laboratory screening, 18 isolates were selected and grouped into two main clusters; cluster 1 containing 12 isolates grown at 43°C, and cluster 2 containing six isolates grown at 37°C. Three natural bacterial consortia with ability to degrade total petroleum hydrocarbons (TPH) were prepared from these isolates. Experiments were conducted in Erlenmeyer flasks under aerobic conditions, with TPH removal percentage varying from 5.9% to 25.1%, depending upon consortia type and concentration. Consortia 7B and 13B exhibited the highest TPH removal percentages of 25% and 23%, respectively before nutrient addition. TPH removal rate was enhanced after addition of nutrients to incubated flasks. The highest TPH reduction (37%) was estimated after addition of a combination of nitrogen, phosphorus and sulphur to consortia 7B. This is the first report concerning biological treatment of total petroleum hydrocarbon by bacteria isolated from the oil refinery plant, where it lay the ground for full integrated studies recommended for hydrocarbon degradation that assist in solving sludge problems.

Microbial degradation of waste hydrocarbons in oily sludge from some Romanian oil fields

During oil production and processing activities, significant quantities of oily sludge are produced. The sludge represents not only an environmental pollution source but also occupies big spaces in storage tanks. Romania, an experienced European oil-producing and processing country, is faced with environmental problems generated by oily sludge accumulations. Many such accumulations are to be submitted to bioremediation processes based on the hydrocarbon degradation activity of naturally occurring, selectively isolated bacteria. In this paper the results concerning a laboratory screening of several natural bacterial consortia and laboratory tests to establish the performance in degradation of hydrocarbons contained in oily sludges from Otesti oil field area, are presented. As a result of the laboratory screening, we selected six natural bacterial consortia (BCSl-I 1 to BCSl-I 6) with high ability in degradation of hydrocarbons from paraffinic and non-paraffinic asphaltic oils (between 25.53%–64.30% for non-paraffinic asphaltic oil and between 50.25%–72.97% for paraffinic oil). The laboratory tests proved that microbial degradation of hydrocarbons contained in oily sludge from Otesti oil field area varied from 16.75% to 95.85% in moving conditions (Erlenmeyers of 750 ml on rotary shaker at 200 rpm) and from 16.85% to 51.85% in static conditions (Petri dishes Ø 10 cm or vessels of 500 ml).

Phytoplankton extracellular release and bacterial growth: dependence on the inorganic N: P ratio

Batch cultures of Chaetoceros affinis grown under nitrogen- (N:P = 5) and phosphorus- (N:P = 100) limited conditions exhibited 30 and 100% higher rates of photosynthetic extracellular release (PER), respectively, than C affims grown under balanced nutrient conditions (N.P = 16). Inoculations of natural bacterial assemblages to PER derived from phytoplankton grown under these different nutrient regimes exhibited highest potential bacterial growth yields (- 46 %) on PER derived from balanced growth. Analysis of the dissolved monomeric (MCHO) and polymeric (PCHO) carbo- hydrate pool and of the dissolved free amino acid (DFAA) fraction of the PER indicated significantly higher specific release rates of these components for phytoplankton grown under P limitation Based on the fluctuation of the MCHO, PCHO and DFAA pool in the batch cultures and on bacterial extra- cellular enzymatic activity (EEA) and bacterial growth yield we have evidence that under P-limited conditions bacteria are not taking up the available carbon efficiently. Bacteria growing on PER derived from N-lmted conditions exhibited high bacterial a- and p-glucosidase activity, while under P limta- tion low EEA was detectable. Extrapolating our results to the severely P-limited summer conditions of the Northern Adriatic Sea, we might conclude that P limitation provokes elevated PER m exponentially growing phytoplankton which is not utilized efficiently by the natural bacterial consortia. This would allow the PER to coagulate and eventually form mucilage.