Biolog GN Plates Research Articles

Inhibitive Bacterial MTT Assay for River Monitoring of Heavy Metals


 An inhibitive assay for metals using a MTT-bacterium assay system is presented. The assay is based on the ability of respiring bacteria to reduce the tetrazolium dye MTT. Out of the 13 metals screened, silver, mercury and copper exhibit strong inhibition to bacterial respiratory activity. The calculated IC50s for silver, mercury and copper were 0.068, 0.092 and 0.517 mg/L, respectively. The IC50 values obtained for these heavy metals are comparable and in certain cases lower than existing bioassay methods such as Daphnia magna, rainbow trout, Microtox™ and papain assays. Works on real water samples from several rivers in Malaysia using the MTT–bacterium assay showed positive correlation with instrumental method (ICP-OES) in detecting heavy metals. The bacterium was tentatively identified as S. marcescens strain Dr.YS8 based on carbon utilization profiles using Biolog GN plates and partial 16s rDNA molecular phylogeny. The system could be used to biomonitor heavy metals extensively in Malaysian waters.

Characterization of A Diesel-Degrading Strain Isolated From A Local Hydrocarbon-Contaminated Site

A diesel-degrading bacterium has been isolated from a primary school soil. The isolate was tentatively identified as Serratia sp. Strain DRY5 based on the carbon utilization profiles using Biolog GN plates and partial 16S rDNA molecular phylogeny. Isolate 5 showed an increase cellular growth with respect to diesel concentrations from 0% until 2% where the optimum growth occurring at 2% (v/v) diesel concentration and was able to tolerate up to 8% (v/v) diesel. Based on the optimization studies using different nitrogen sources, Ammonium chloride proved to be the best nitrogen source. Ammonium chloride was optimum at 7.7 gl-1 and concentrations higher than that resulted with inhibiton of the cellular growth. The optimal temperature and the optimal pH that supported the growth of this bacterium was between 23 to 40 oC and pH 7.5 to pH 8.5 respectively. Diesel components was proven to be completely removed from the reduction in the hydrocarbon peaks monitored by Solid Phase Microextraction Gas Chromatography analysis after 7 days of incubation.All of these characteristics suggest that this bacterium is the right bacterium for bioremediation of diesel spills and pollution in the tropics.

Isolation and Characterization of A Heavy Metal-Tolerant Diesel Oil - Degrading Strain


 A diesel-degrading bacterium has been isolated from a local university soil. The isolate was tentatively identified as Burkholderia sp. strain DRY27 based on the carbon utilization profiles using Biolog GN plates and partial 16S rDNA molecular phylogeny. Isolate 27 showed an increase cellular growth with respect to diesel concentrations from 0% until 3% where the optimum growth occurring at 3% (v/v) diesel concentration. Based on the optimization studies, sodium nitrate proved to be the best nitrogen source. Sodium nitrate was optimum at 7.7 gl-1 .The optimal temperature and optimal pH for this bacterium was between 10 to 40 oC and pH 7.5 to pH 8.5 respectively. Diesel components was proven to be completely removed from the reduction in the hydrocarbon peaks monitored by Solid Phase Microextraction Gas Chromatography analysis. These prove that this bacterium is the right bacterium for bioremediation of diesel spills and pollution in the tropics.

Photobacterium aphoticum sp. nov., isolated from coastal water

A facultatively anaerobic marine gammaproteobacterium, designated strain M46(T), was isolated from Mediterranean seawater at Malvarrosa beach, Valencia, Spain. The strain was characterized by using a polyphasic approach and was found to be situated within the genus Photobacterium in the family Vibrionaceae. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain M46(T) was closely related to P. rosenbergii CECT 7644(T), P. halotolerans CECT 5860(T) and P. ganghwense CECT 7641(T), showing sequence similarities of 96.8, 96.4 and 96.2 %, respectively. According to the results of phylogenetic analyses based on recA and gyrB gene sequences, the most closely related taxon was P. ganghwense CECT 7641(T) with 87.4 and 85.0 % sequence similarity, respectively. Regardless of the gene used in phylogenetic analysis, strain M46(T) always formed a separate and stable clade containing these three species of the genus Photobacterium. Strain M46(T) was not luminescent and produced a diffusible brown pigment. It required NaCl to grow, reduced nitrate to nitrite and oxidized a small number of substrates in Biolog GN plates. Strain M46(T) was positive for arginine dihydrolase (ADH), β-galactosidase, aesculin hydrolysis and DNase activity. In API ZYM tests, the novel strain was positive for alkaline phosphatase, leucine arylamidase and acidic phosphatase activities. The major cellular fatty acids were unsaturated C(18) and C(16), as in other members of the genus Photobacterium, but their relative amounts and the presence or absence of other fatty acids differentiated strain M46(T) from its closest relatives. Based on the results of this polyphasic taxonomic study, strain M46(T) represents a novel species of the genus Photobacterium, for which the name Photobacterium aphoticum is proposed. The type strain is M46(T) ( = CECT 7614(T) = KCTC 23057(T)).

Hexavalent molybdenum reduction to Mo-blue by Acinetobacter calcoaceticus

A local molybdenum-reducing bacterium was isolated and tentatively identified as Acinetobacter calcoaceticus strain Dr.Y12 based on carbon utilization profiles using Biolog GN plates and 16S rDNA comparative analysis. Molybdate reduction was optimized under conditions of low dissolved oxygen (37 degrees C and pH 6.5). Of the electron donors tested, glucose, fructose, maltose and sucrose supported molybdate reduction after 1 d of incubation, glucose and fructose supporting the highest Mo-blue production. Optimum Mo-blue production was reached at 20 mmol/L molybdate and 5 mmol/L phosphate; increasing the phosphate concentrations inhibited the production. An increase in an overall absorption profiles, especially at peak maximum at 865 nm and the shoulder at 700 nm, was observed in direct correlation with the increased in Mo-blue amounts. Metal ions, such as chromium, cadmium, copper, mercury and lead (2 mmol/L final concentration) caused approximately 88, 53, 80, 100, and 20 % inhibition, respectively. Respiratory inhibitors, such as antimycin A, rotenone, sodium azide and cyanide showed in this bacterium no inhibition of the Mo-blue production, suggesting that the electron transport system is not a site of molybdate reduction.

Molybdate reduction byPseudomonassp. strain DRY2

To isolate and characterize a potent molybdenum-reducing bacterium. A minimal salt medium supplemented with 10 mmol l(-1) molybdate, glucose (1.0%, w/v) as a carbon source and ammonium sulfate (0.3%, w/v) as a nitrogen source was used in the screening process. A molybdenum-reducing bacterium was isolated and tentatively identified as Pseudomonas sp. strain DRY2 based on carbon utilization profiles using Biolog GN plates and partial 16S rDNA molecular phylogeny. Strain DRY2 produced 2.4, 3.2 and 6.2 times more molybdenum blue compared to Serratia marcescens strain DRY6, Enterobacter cloacae strain 48 and Eschericia coli K12, respectively. Molybdate reduction was optimum at 5 mmol l(-1) phosphate. The optimum molybdate concentration that supported molybdate reduction at 5 mmol l(-1) phosphate was between 15 and 25 mmol l(-1). Molybdate reduction was optimum at 40 degrees C and at pH 6.0. Phosphate concentrations higher than 5 mmol l(-1) strongly inhibited molybdate reduction. Inhibitors of electron transport system such as antimycin A, rotenone, sodium azide and cyanide did not inhibit the molybdenum-reducing enzyme activity. Chromium, copper, mercury and lead inhibited the molybdenum-reducing activity. A novel molybdenum-reducing bacterium with high molybdenum reduction capacity has been isolated. Molybdenum is an emerging global pollutant that is very toxic to ruminants. The characteristics of this bacterium suggest that it would be useful in the bioremediation of molybdenum pollutant.

Reduction of molybdate to molybdenum blue by Enterobacter sp. strain Dr.Y13

Extensive use of metals in various industrial applications has caused substantial environmental pollution. Molybdenum-reducing bacteria isolated from soils can be used to remove molybdenum from contaminated environments. In this work we have isolated a local bacterium with the capability to reduce soluble molybdate to the insoluble molybdenum blue. We studied several factors that would optimize molybdate reduction. Electron donor sources such as glucose, sucrose, lactose, maltose and fructose (in decreasing efficiency) supported molybdate reduction after 24 h of incubation with optimum glucose concentration for molybdate reduction at 1.5% (w/v). The optimum pH, phosphate and molybdate concentrations, and temperature for molybdate reduction were pH 6.5, 5.0, 25 to 50 mM and 37 degrees C, respectively. The Mo-blue produced by cellular reduction exhibited a unique absorption spectrum with a maximum peak at 865 nm and a shoulder at 700 nm. Metal ions such as chromium, cadmium, copper, silver and mercury caused approximately 73, 71, 81, 77 and 78% inhibition of the molybdenum-reducing activity, respectively. All of the respiratory inhibitors tested namely rotenone, azide, cyanide and antimycin A did not show any inhibition to the molybdenum-reducing activity suggesting components of the electron transport system are not responsible for the reducing activity. The isolate was tentatively identified as Enterobacter sp. strain Dr.Y13 based on carbon utilization profiles using Biolog GN plates and partial 16S rDNA molecular phylogeny.

Identification of Vibrio harveyi isolated from diseased cultured wedge sole Dicologoglossa cuneata

We report the first isolation of Vibrio harveyi from wedge sole Dicologoglossa cuneata. The pathogen was recovered from ulcers and internal organs of ailing cultured fish, from 7 different outbreaks between 2004 and 2006. The 15 isolates found were phenotypically characterized using biochemical tests and BIOLOG GN plates, which revealed high phenotypic diversity. Diagnosis was confirmed with PCR using V harveyi specific primers and partial 16S and 23S rRNA gene sequencing. A virulence evaluation of the isolates was also performed using fry and juvenile wedge sole. Significant mortalities were recorded by intraperitoneal injection; however, no mortalities were recorded by bath immersion.

Bacterial reduction of hexavalent molybdenum to molybdenum blue

A bacterium that was able to tolerate and reduce as high as 50 mM of sodium molybdate to molybdenum blue has been isolated from a metal recycling ground. The isolate was tentatively identified as Serratia sp. strain Dr.Y8 based on the carbon utilization profiles using Biolog GN plates and partial 16S rDNA molecular phylogeny. ANOVA analysis showed that isolate Dr.Y8 produced significantly higher (P < 0.05) amount of Mo-blue with 3, 5.1 and 11.3 times more molybdenum blue than previously isolated molybdenum reducers such as Serratia marcescens strain Dr.Y6, E. coli K12 and E. cloacae strain 48, respectively. Its molybdate reduction characteristics were studied in this work. Electron donor sources such as sucrose, mannitol, fructose, glucose and starch supported molybdate reduction. The optimum phosphate, pH and temperature that supported molybdate reduction were 5 mM, pH 6.0 and 37°C, respectively. The molybdenum blue produced from cellular reduction exhibited a unique absorption spectrum with a maximum peak at 865 nm and a shoulder at 700 nm. Metal ions such as chromium, silver, copper and mercury resulted in approximately 61, 57, 80, and 69% inhibition of the molybdenum-reducing activity at 1 mM, respectively. The reduction characteristics of strain Dr.Y8 suggest that it would be useful in future molybdenum bioremediation.

Hexavalent Molybdenum Reduction to Molybdenum Blue by S. Marcescens Strain Dr. Y6

A molybdate-reducing bacterium has been locally isolated. The bacterium reduces molybdate or Mo(6+) to molybdenum blue (molybdate oxidation states of between 5+ and 6+). Different carbon sources such as acetate, formate, glycerol, citric acid, lactose, fructose, glucose, mannitol, tartarate, maltose, sucrose, and starch were used at an initial concentration of 0.2% (w/v) in low phosphate media to study their effect on the molybdate reduction efficiency of bacterium. All of the carbon sources supported cellular growth, but only sucrose, maltose, glucose, and glycerol (in decreasing order) supported molybdate reduction after 24 h of incubation. Optimum concentration of sucrose for molybdate reduction is 1.0% (w/v) after 24 h of static incubation. Ammonium sulfate, ammonium chloride, valine, OH-proline, glutamic acid, and alanine (in the order of decreasing efficiency) supported molybdate reduction with ammonium sulfate giving the highest amount of molybdenum blue after 24 h of incubation at 0.3% (w/v). The optimum molybdate concentration that supports molybdate reduction is between 15 and 25 mM. Molybdate reduction is optimum at 35 degrees C. Phosphate at concentrations higher than 5 mM strongly inhibits molybdate reduction. The molybdenum blue produced from cellular reduction exhibits a unique absorption spectrum with a maximum peak at 865 nm and a shoulder at 700 nm. The isolate was tentatively identified as Serratia marcescens Strain Dr.Y6 based on carbon utilization profiles using Biolog GN plates and partial 16s rDNA molecular phylogeny.

Soil Microbial Community Response to Hexavalent Chromium in Planted and Unplanted Soil

Theories suggest that rapid microbial growth rates lead to quicker development of metal resistance. We tested these theories by adding hexavalent chromium [Cr(VI)] to soil, sowing Indian mustard (Brassica juncea), and comparing rhizosphere and bulk soil microbial community responses. Four weeks after the initial Cr(VI) application we measured Cr concentration, microbial biomass by fumigation extraction and soil extract ATP, tolerance to Cr and growth rates with tritiated thymidine incorporation, and performed community substrate use analysis with BIOLOG GN plates. Exchangeable Cr(VI) levels were very low, and therefore we assumed the Cr(VI) impact was transient. Microbial biomass was reduced by Cr(VI) addition. Microbial tolerance to Cr(VI) tended to be higher in the Cr-treated rhizosphere soil relative to the non-treated systems, while microorganisms in the Cr-treated bulk soil were less sensitive to Cr(VI) than microorganisms in the non-treated bulk soil. Microbial diversity as measured by population evenness increased with Cr(VI) addition based on a Gini coefficient derived from BIOLOG substrate use patterns. Principal component analysis revealed separation between Cr(VI) treatments, and between rhizosphere and bulk soil treatments. We hypothesize that because of Cr(VI) addition there was indirect selection for fast-growing organisms, alleviation of competition among microbial communities, and increase in Cr tolerance in the rhizosphere due to the faster turnover rates in that environment.

소독제에 따른 생물막 살균효율과 생물막 미생물집단의 탄소이용능 비교

수돗물에서 생성된 탄소강관위의 생물막에 유리잔류염소와 모노클로라민을 처리하여 세균농도 변화와 그에 따른 탄소원 이용능을 조사하였다. 소독제 농도를 단계적으로 올렸을 때 종속영양세균의 농도는 모노클로라민과 유리잔류염소의 농도가 각 1.5, 1.0 mg/l까지는 대조구에 비해 감소가 없었지만 (P = 0.56, ANOVA) 모노클로라민 2.0 mg/l, 유리잔류염소 1.5 mg/l 일때 감소되었다 (P < 0.01, ANOVA). 소독제의 농도를 단계적으로 높일때 세균활성의 증가 후 감소 그리고 세균농도의 감소가 관찰되었다. 세균농도가 유사하더라도 각 탄소원에 대한 정량적, 정성적 이용도가 서로 달라 군집구조가 상이할 것으로 생각되었다. The influence of disinfectant on bacterial concentration and carbon usage patterns by Biolog GN plates were investigated for biofilm on carbon steel pipe. Heterotrophic bacterial concentrations were not different among non-, monochloramine- (1.0, 1.5 mg/l) and free chlorine- (0.5, 1.0 mg/l) treated samples (P = 0.56, ANOVA). However treatment of 1.5 mg/l free chlorine and 2.0 mg/l monochloraime showed significantly lower densities than control (P < 0.01, ANOVA). By the stepwise increasement of disinfectant concentration, the carbon usage activities of biofilm microflora were decreased after increase without the decrease of bacterial concentration, following reduction of cell density. Carbon usage patterns were qualitatively and quantitatively different with similar bacterial concentrations. Principal component analysis suggested that type and concentration of disinfectant were main factors on the usage of carbons. Our result suggest that the differences of bacterial communities were different among the samples and the need of monochloramine for the reduction of biofilm in drinking water.

Early colonization of barley roots by Pseudomonas fluorescens studied by immunofluorescence technique and confocal laser scanning microscopy

Highly specific polyclonal antibodies against two Pseudomonas fluorescens strains (DF57 and Ag1), which differed by approximately 10% of their utilizable substrates as tested in Biolog GN plates, were used for in situ labelling of bacterial cells colonizing barley roots grown in sterile soil. By using a confocal laser scanning microscope single bacteria of both strains could be detected on the roots. Seed-inoculated bacteria rapidly colonized the root surface (rhizoplane) by active migration; after 1 day the anterior part of the root was densely covered by bacteria occupying the crevices between epidermal root cells. As the roots became longer, this bacterial population in the rhizoplane formed long strings of closely associated cells. After 7 days, however, the rhizoplane population of string-forming cells was partially detached developing a patchy distribution along the root; a separate population of cells localized in the slime matrix (mucigel) surrounding the root was well developed at this time. Using two different fluorochromes attached to the antibodies, the two strains could be detected simultaneously in co-inoculation experiments. The recordings, however, gave no indications of competition between the two strains during root colonization.

Separation power of the 95 substrates of the BIOLOG system determined in various soils

The separation power of the 95 substrates of the BIOLOG GN plates was tested using soil from Denmark, Germany and Italy. The data set comprised 420 BIOLOG plates, 195 of them incubated at 14°C and 225 incubated at 30°C. We calculated the ratio of the between soil variation to the within soil variation of each substrate to obtain two lists of carbon sources ranked according to their separation power. These results suggest that the use of a reduced set of discriminating carbon sources, with a higher number of replicates on each plate, would be a better approach because statistical tests like MANOVA and related techniques can be applied.

Comparison of soil microbial community between soils amended with or without farmyard manure

Comparison of microbial properties were made between soils amended with chemical fertilizer (CF-soil) and with CF and farmyard manure (FYM: CF + FYM-soil) for more than 10 years in an attempt to elucidate microbiological characteristics of the soil with the repeated application of FYM. The numbers of total bacteria were not significantly different between the CF- and CF + FYM-soils, while those of culturable bacteria were two to six times higher in the CF + FYM-soil than in the CF-soil. Microbial community structure on a broad scale was estimated by molecular methods: %G + C profiles of soil community DNA and sequencing of 16S rDNA of clones. There was a shift in the %G + C profiles toward a greater proportion of higher %G + C classes in the CF + FYM-soil. 16S rDNA clone library was obtained from the community DNA of the two soils and phylogenetic analysis of 77 clones was made. While 16S rDNA clones in the CF-soil were dominated by alpha-, gamma- and beta- proteobacteria (36, 28 and 10%, respectively), those in the CF + FYM-soil by gamma- and alpha- proteobacteria, Actinobacteria and Acidobacterium (26, 21, 13 and 11%, respectively). Phospholipid fatty acid analysis (PLFA) showed a seasonal variation in the soil microbial community structure, but clearly differentiated the CF + FYM-soil from the CF-soil. These results suggested that different soil microbial community structure developed by the repeated application of FYM. Carbon utilization profiles using Biolog GN plates showed that the CF + FYM-soil had a higher utilization ability of the substrates, especially l-proline and phenyl ethylamine, α-cyclodextrin, cellobiose and d-serine. Microbial community specific to soil amended with FYM is discussed in a combination with the results obtained by the different methods.

The influence of high application rates of polyacrylamide on microbial metabolic potential in an agricultural soil

Water soluble anionic polyacrylamide (PAM) is a highly effective erosion preventing and infiltration enhancing polymer, when applied at rates of 1–10 g m −3 in furrow irrigation water. PAM greatly reduces sediment, nutrients, pesticides and coliform bacteria in irrigation runoff. There has been some concern about the potential for PAM accumulation to affect microbial ecology. We ran a long-term study applying massive quantities of PAM to soil and monitored its impact on soil microbial potential. In June, July and August, we measured active soil bacterial and fungal biomass and microbial diversity in soils receiving 0 (control), 2691 and 5382 kg active ingredient (ai) PAM ha −1. Active bacterial biomass in soil was 20–30% greater in the control treatment than in soil treated with 2691 or 5382 kg ai PAM ha −1 in June and August, but not July. Active fungal biomass in soils was 30–50% greater in the control treatment than soil treated with 2691 or 5382 kg ai PAM ha −1 in June and July, but not August. Active microbial biomass in soil was 27–48% greater in the untreated control than soil treated with 2691 or 5382 kg ai PAM ha −1 except in June. Whole soil fatty acid profiles showed no discernible change in the soil microbial community due to either of the PAM treatments at any sampling time. Analysis of nutritional characteristics using Biolog GN plates, however, yielded an apparent separation of the non-amended control soils from those plots receiving the high PAM application rate in June, but not in July or August. In contrast, comparisons of the three sampling times by both the fatty acid and Biolog analyses indicated that the microbial metabolic potential present in June were different from those sampled in July and August. Although PAM application to soil or irrigation water in some cases may reduce active bacterial and fungal biomass it does not seem to appreciably affect the soil microbial metabolic potential.

Vibrio splendidus biotype 1 as a cause of mortalities in hatchery-reared larval turbot, Scophthalmus maximus (L.)

To characterize bacteria associated with turbot larvae feeding on Artemia and identify pathogens causing mortalities in larvae. To identify bacteria associated with mortalities in larval turbot rearing, bacteria were isolated from homogenates of Artemia or from several batches of well-performing or poorly performing turbot larvae. Samples were plated onto marine agar and were characterized using biochemical tests and BIOLOG GN plates. Total culturable aerobic bacteria ranged from 1.9 x 10(5) to 1.8 x 10(6) CFU per larva and >96% of bacteria identified were vibrios. Almost all bacteria were haemolytic and clustered into two phenons represented by Vibrio alginolyticus and Vibrio splendidus. The bacterial flora of Artemia was almost entirely V. alginolyticus, whereas V. splendidus biotype 1 dominated the larval turbot gut flora (69/115 isolates in seven experiments) and formed four different groups based on BIOLOG GN reactions. Of 16 isolates tested for virulence towards turbot larvae, four of the 11 V. splendidus biotype 1 isolates were lethal and all belonged to the same group of V. splendidus biotype 1 isolates. In a commercial turbot hatchery, the microbial flora of the larval gut was dominated by V. splendidus biotype 1. Four of the 11 V. splendidus biotype 1 isolates caused mortalities in larval turbot and all belonged to one group of the biotype 1 strains identified. Identification of four isolates of V. splendidus that are pathogenic for turbot larvae from three separate batches of larval turbot will allow these to be compared with avirulent isolates to define how V. splendidus causes mortalities in larval turbot.

수돗물속에서 관재질에 따른 생물막의 CLPP

The effect of pipe materials on biofilm communities were investigated by CLPP (community level physiology profile) using Biolog GN plates. Heterotrophic bacterial concentrations were and there was no differences between galvanized iron and carbon steel. Average optical density of Biolog plate was similar between two pipe materials. However, CLPP was different according to the type of pipe materials and exposed times to tap water, and CLPP was independent of bacterial concentration. This represents the differences of bacterial communities with pipes and water contact times.

Microbial and biochemical soil quality indicators and their potential for differentiating areas under contrasting agricultural management regimes

The aim of this study was to examine interrelationships between functional biochemical and microbial indicators of soil quality, and their suitability to differentiate areas under contrasting agricultural management regimes. The study included five 0.8ha areas on a sandy-loam soil which had received contrasting fertility and cropping regimes over a 5 year period. These were organically managed vegetable, vegetable–cereal and arable rotations, an organically managed grass clover ley, and a conventional cereal rotation. The organic areas had been converted from conventional cereal production 5 years prior to the start of the study. All of the biochemical analyses, including light fraction organic matter (LFOM) C and N, labile organic N (LON), dissolved organic N and water-soluble carbohydrates showed significant differences between the areas, although the nature of the relationships between the areas varied between the different parameters, and were not related to differences in total soil organic matter content. The clearest differences were seen in LFOM C and N and LON, which were higher in the organic arable area relative to the other areas. In the case of the biological parameters, there were differences between the areas for biomass-N, ATP, chitin content, and the ratios of ATP: biomass and basal respiration: biomass. For these parameters, the precise relationships between the areas varied. However, relative to the conventionally managed area, areas under organic management generally had lower biomass-N and higher ATP contents. Arbuscular mycorrhizal fungus colonization potential was extremely low in the conventional area relative to the organic areas. Further, metabolic diversity and microbial community level physiological profiles, determined by analysis of microbial community metabolism using Biolog GN plates and the activities of eight key nutrient cycling enzymes, grouped the organic areas together, but separated them from the conventional area. We conclude that microbial parameters are more effective and consistent indicators of management induced changes to soil quality than biochemical parameters, and that a variety of biochemical and microbial analyses should be used when considering the impact of management on soil quality.

Biolog for the determination of diversity in microbial communities

Diversity and dynamics of microbial communities have been analysed by culture-dependent methods, which exclude the majority of fastidious microbes due to the selective nature of the media. Molecular methods have been used to determine diversity of microbial communities, but indicate the genetic complexity within a community. An alternative approach is to examine components of functional biodiversity (i.e. substrate utilisation), for which there exists a reasonable chance of detecting patterns, which could be related to the functional diversity of the species present in the community. In this study, different carbon source profiles were generated by inoculating Biolog GN and GP microtitre plates, with different dilutions of microbial communities. The high number of substrates utilised at the lower dilutions (10-1 and 10-2) indicated a high functional diversity in the communities tested. This, however, did not necessarily reflect the evenness of the functionality. Functional evenness of each species was reflected upon further dilution. Our results indicated differences in the functional diversity of the microbial communities amongst some of the natural environments studied. The results indicated that evenness and dominance can be demonstrated by mixtures of cultures as well as in natural environments. WaterSA Vol.28(1) 2002: 29-36