Heterotrophic Bacterial Populations Research Articles

Heterotrophic bacterial populations in the mineral waters of thermal springs in Spain.

The microbiological quality and heterotrophic bacterial populations of 26 thermal mineral water springs in Spain were studied. In most of the springs the number of viable aerobes was less than 10(3) cfu ml-1 and the number of sporulated bacteria less than 10(2) cfu ml-1. No significant differences were found in the counts obtained with Plate Count Agar (PCA) and PCA diluted 1:10 and incubated at 22 degrees, 37 degrees and 45 degrees C. Total coliforms were found in 14 springs, faecal streptococci in three, spores of sulphite-reducing Clostridium and Pseudomonas aeruginosa in seven. Neither Escherichia coli nor Staphylococcus aureus were found. A total of 665 strains were isolated and 85.4% of these identified; 329 were Gram-positive and 239 were Gram-negative. The genera most prevalent present in the springs were Pseudomonas (in 92.3%), Bacillus (65.4%), Enterobacter, Micrococcus and Staphylococcus (50%), Acinetobacter (42.3%), Arthrobacter (38.4%), Clostridium (27%) and Xanthomonas (23%). Gram-negative bacteria predominated in the mesothermal springs and Gram-positive bacteria in the hyper- and hypothermal springs. The most common Gram-negative rod species isolated were Ps. fluorescens, Ps. aeruginosa, Ps. putida, Ent. agglomerans, Ent. sakazakii, Ac. calcoaceticus and Ent. amnigenus.

Gut microflora of the larva of silkworm, Bombyx mori

The quantitative and qualitative changes of bacterial flora associated with the silkworm (Bombyx mori) at different stages of its life cycle were studied. Larvae reared on mulberry leaves were dissected and their bacterial populations counted after a 3-day incubation period at 28 ± 2°C. The results showed a higher heterotrophic bacterial population in the fourth and the fifth instars, which coincide with the active feeding stage of the larvae. The similarity of the genera observed in the digestive tract and that observed on the leaves fed to the larvae suggests colonisation of food microflora in the gut following ingestion. The bacteria inhabiting the gut of silkworm were found to be elaborating amylase, caseinase, gelatinase, lipase and urease. The highest percentage of isolates were protease producers followed by lipid and polysaccharide splitters. The results indicate that the bacterial flora play an important role in the digestion of ingested food material.

Influence of phytoplankton lysis or grazing on bacterial metabolism and trophic relationships

Experimental microcosms were used to study the dynamics of heterotrophic bacterial populations with respect to phytoplankton loss. In a two-stage linked culture system, we artificially separated production and loss processes of a diatom Phaeodactylum tricornutum. In the first (productive) stage, the algae developed axenically and continuously. The outflow was fluxed in two degradation stages, where phytoplankton-derived detritus resulted respectively from: (1) excretion and by-products of phagotrophic organisms (protozoans), and (2) bacterial degradation through bacterial attachment and lysis. According to the phytoplankton decay mode, i.e., lysis or grazing, bacterial adaptations were different. The study of bacterial productivity and aminopeptidase activity showed specific bacterial evolution during the succession of different prey-predator relationships. The occurrence of aggregates allowed nanoflagellates to develop an alternative diet; they fed not only on bacteria, but also on partially degraded phytoplankton detritus, inducing a strong short-cut in the food chain. Sources and controls of extracellular proteolytic activity are discussed. Such experimental approaches are interesting because they separate bacterial lysis and protozoan grazing of phytoplankton, as well as the fates of their corresponding phytoplankton detritus in the microbial food web.

Denitrification and methane production in sediment of Hamilton Harbour (Canada)

Systematic sampling of 21 sites covering Hamilton Harbour (Lake Ontario, Canada) was carried out during the summer in 1990 and 1991 in order to study how well environmental factors, such as O2, NO 3 (-) , and organic carbon, and the spatial structure can explain observed variation of potential denitrification, CH4 and CO2 production, as well as N2 fixation in sediment slurries. Using canonical redundancy analysis and an extension of this method to partial out the variance into spatial and environmental components, we found that most of the explained fraction of potential microbial activities (70-90%) was accounted for by the significant environmental variables (NH 4 (+) , particulate carbon, dissolved organic carbon, dissolved O2, depth, and temperature) and not much by the spatial polynomial trend surface. We found significant path coefficients (0.53 and 0.57 in 1990 and 1991) between CO2 production and potential denitrification, which suggests that denitrifiers are dependent upon a heterotrophic bacterial population for directly assimilable carbon sources. We also found significant path coefficients between particulate carbon and both CH4 production (0.67 and 0.33) and CO2 production (0.50 and 0.38), while significant path coefficients were also found between dissolved organic carbon and CO2 production (0.34 and 0.47). We conclude that beside well-known abiotic factors such as O2, NO 3 (-) , and organic carbon, a biotic factor involved in carbon metabolism may be important in explaining the spatial variation of denitrification capacity in the sediment of Hamilton Harbour.

Seasonal ecology of hydrocarbon-utilizing microbes in the surface Waters of a river

Seasonal changes in the microbial communities of the New Calabar Riverwater have been investigated. Analyses of the BOD, pH, salinity, oil and grease levels of effluents of industries sited along the river were also conducted. High hydrocarbon-utilizing microbial populations were found. The percentage of hydrocarbon-utilizing heterotrophic bacteria ranged between 0-98% and 0-68% in the rainy and dry months, respectively. Counts of hydrocarbon-utilizing actinomycetes in the rainy months ranged between 0-95% and 2-55% in the dry months. The hydrocarbon-utilizing yeast population ranged between 1-95% and 2-85% for the rainy and dry months, respectively. Rainy month values for hydrocarbon-utilizing mould population ranged from 0-17% while dry month values ranged from 0-47%. The hydrocarbon-utilizing cyanobacterial population ranged between 0-95% and 0-33% in the rainy and dry months, respectively. Our results suggest that the heterotrophic bacterial and cyanobacterial populations are higher in the rainy months than in the dry months. However, the hydrocarbon-utilizing yeast, mould and actinomycete populations did not show seasonal variation.

Population biology of Bacillus cereus UW85 in the rhizosphere of field-grown soybeans

We studied the spatial and temporal distribution and abundance of the biocontrol agent Bacillus cereus UW85 in the rhizosphere of soybeans during two growing seasons in the field. For this study, we used a neomycin-resistant mutant, UW85nl, derived from UW85. UW85nl spores were applied to seeds and by 24 h after planting 72% of the spores had germinated. UW85nl colonized emerging radicles, but populations were 10–50-fold smaller on radicles than they were on seeds at planting. UW85nl population sizes in the rhizosphere of 10–35-day old plants were largest near the crown of the plant and smaller further from the crown. For example, in a 1989 experiment 21 days after planting, UW85nl populations were 158-fold larger 0–2 cm below the crown than they were 7–8 cm below the crown. UW85nl population sizes were largest right after planting, and by seed harvest they decreased to levels comparable to indigenous B. cereus populations on untreated roots; however, at harvest the entire B. cereus population on treated roots was neomycin resistant, whereas on untreated roots < 3% was neomycin resistant. The proportion of the heterotrophic bacterial population that was represented by UW85n 1 was generally largest right after planting and decreased at subsequent sampling times. Our results indicate that UW85nl grew and spread on soybean roots, and it persisted in the rhizosphere until seed harvest.

Spatial Distribution Patterns of Heterotrophic Bacterial Population in a Coastal Ecosystem (Thau basin, France)

The abundances of culturable heterotrophic bacterial populations on the scale of a coastal ecosystem (Thau basin, France) were measured by systematic sampling at 63 stations in all four seasons. Distribution maps produced by the 'kriging' method indicate that bacterial distribution patterns correspond to gradients that decrease from points of continental water input and extend for 2 to 10 km. Variograms were used to analyse variance of abundances with distance and to classify distribution patterns according to local and large-scale variance. The mean abundances of bacteria in the waters of the ecosystem appeared to depend on fluctuations of watershed inputs. The heterogeneity of abundances was affected by fluctuations in wind speed and the related changes in convective and advective currents. Estimations of local and larger-scale variance can also be useful in determining the most suitable sampling strategies for describing and analysing the distribution of bacteria in aquatic ecosystems.

Flow Cytometric Analysis of Marine Bacteria with Hoechst 33342

We investigated the accuracy and precision of flow cytometric (FCM) estimates of bacterial abundances using 4', 6-diamidino-2-phenylindole (DAPI) and Hoechst 33342 (HO342, a bisbenzamide derivative) on paraformaldehyde-fixed seawater samples collected from two stations near Oahu, Hawaii. The accuracy of FCM estimates was assessed against direct counts by using epifluorescence microscopy. DAPI and HO342 differ in two aspects of their chemistry that make HO342 better suited for staining marine heterotrophic bacteria for FCM analysis. These differences are most important in studies of open-ocean ecosystems that require dual-beam FCM analysis to clearly separate heterotrophic bacterial populations from populations of photosynthetic Prochlorococcus spp. Bacterial populations were easier to distinguish from background fluorescence when stained with HO342 than when stained with DAPI, because HO342 has a higher relative fluorescence quantum yield. A substantially higher coefficient of variation of blue fluorescence, which was probably due to fluorescent complexes formed by DAPI with double-stranded RNA, was observed for DAPI-stained populations. FCM estimates averaged 2.0 and 12% higher than corresponding epifluorescence microscopy direct counts for HO342 and DAPI-stained samples, respectively. A paired-sample t test between FCM estimates and direct counts found no significant difference for HO342-stained samples but a significant difference for DAPI-stained samples. Coefficients of variation of replicate FCM abundance estimates ranged from 0.63 to 2.9% (average, 1.5%) for natural bacterial concentrations of 6 x 10 to 15 x 10 cells ml.

Response of a freshwater bacterial community to mercury contamination (HgCl2 and CH3HgCl) in a controlled system

An experimental study was made on the effects of inorganic mercury (HgCl2) and methylmercury (CH3HgCl) on freshwater aerobic heterotrophic bacterial population. The experimental system was based on two-compartment biotopes: natural sediment, from the Garonne River, and dechlorinated tap water. The response of bacterial communities to mercury additions (to the water column) was monitored by determining total Hg in water and enumerating the total number of bacteria and the evolution of the mercury resistant community. Isolation was carried out by plate count method. Enumeration of mercury resistant strains was made with a general medium (Iron-Tryp-tone agar) amended with 10 μg Hg/ml of HgCl2. The response to 2 μg Hg/L (HgCl2) was fast approximately 50% of the maximum percentage of mercury resistant bacteria being reached after one hour (21.7% after 17 h exposure). Spikes of CH3HgCl (2 μg Hg/L) in the water column caused an initial inhibition of growth of Hg-resistant and sensitive bacteria followed by a complete recovery of the background microbial population after 84 h. Seven mercury resistant bacterial strains were isolated from the experimental systems and each of them was checked for HgCl2 and CH3HgCl transformation. All were able to volatilize HgCl2 by producing elemental mercury, but none was able to degrade methylmercury. Additions of different concentrations of HgCl2 (0.02 μg Hg/L to 2 μg Hg/L) to the water column caused a proportional increase in the percentage of mercury-resistant bacteria. Low concentrations (<0.6 μg Hg/L) of CH3HgCl also induced the Hg-resistant community, whereas 2 μg Hg/L of CH3HgCl inhibited the growth of both Hg-sensitive and Hg-resistant heterotrophic bacteria.

Correlations between Heterotrophic Bacterial Populations and Water Quality Variables in Stream Waters.

Heterotrophic bacterial populations in a total of 22 stream waters polluted in different degrees were investigated by analyzing correlations with water quality variables. Colony-forming units on polypeptone-yeast extract-glucose agar plates correlated significantly with the concentrations of suspended solids, chemical oxygen demand and total organic carbon. Four hundred and thirty-four strains isolated from 22 stream waters were classified into 60 types according to the characteristics of colony color, motility, Gram stain, catalase production, oxidase production and oxidation-fermentation (O-F) test. In relationships between the percentage of the 60 types of isolates and water quality variables, YA1, YI, and NPG type positively, and NPK type negatively correlated significantly with many of the variables. All of these bacterial types were Gram negative bacteria ; the YA1 type was a yellow pigmented, non-motile, catalase-positive, oxidasenegative and O-F test-negative bacterium (Flavobacterium sp.) ; the YI type was a yellow pigmented, motile, catalase-positive, oxidase-negative and O-F test-negative bacterium (Pseudomonas sp.) ; the NPG type was a non-pigmented, motile, catalase-and oxidasepositive, and O-F test-oxidative bacterium (Pseudomonas sp.) ; and the NPK type, a non-pigmented, motile, catalase-negative, oxidase-positive and O-F test-negative bacterium (unknown sp.). These results suggest that YA1, YI and NPG types may be present predominantly in polluted waters and the NPK type in non-polluted waters, that is, that they may be good candidates as pollution indicators. The percentages of total YA1, YI and NPG types correlated strongly with most of the water quality variables.

The distribution of dissolved DNA in an oligotrophic and a eutrophic river of Southwest Florida

The distribution of dissolved DNA concentrations and some microbial variables were compared in an oligo-mesotrophic river (the Crystal River) and a phosphate-rich eutrophic river (the Alafia River) in Southwest Florida over a 15 month period. Concentrations of phosphate and nitrate in the Alafia River averaged 135 and 18.2 times the respective phosphate and nitrate concentrations of the oligo-mesotrophic Crystal River. The seasonal average dissolved DNA concentration for the Alafia River exceeded that of the Crystal River by a factor of 1.8 (8.2 μg 1−1 compared to 4.6 μg 1−1, respectively). The greatest concentrations of dissolved DNA in the Alafia River were found in areas that contained the largest populations of phytoplankton and bacteria (a reservoir formed from an abandoned phosphate mining pit and two downstream stations near the mouth of the river). Differences in dissolved DNA concentrations between these environments and more pristine environments (i.e. all Crystal River Stations and upstream Alafia River stations) were of the same order of magnitude (1.8 to 2.2-fold) as the differences in bacterial abundance and activity, but considerably less than differences in phytoplankton abundance and activity between such environments. Seasonal variations in dissolved DNA concentrations in the Crystal River corresponded to seasonal variations in microbial populations, with minimal values in January and greater values in July. In the Alafia River, lowest concentrations for dissolved DNA occurred in July during the wet season, when seasonal flooding of area of leaf litter yielded high levels of dissolved organic carbon (DOC) which were low in dissolved DNA. These results suggest that: 1) in situ planktonic activity is a greater source of dissolved DNA than allochthonous or terrestrial sources of DOC; 2) factors that control the magnitude of heterotrophic bacterial populations are more likely to control dissolved DNA levels than factors regulating autotrophic population activity and abundance; 3) differences in dissolved DNA between eutrophic and oligo-mesotrophic environments are often much smaller than the differences in nutrient concentration between such environments.

Alterations in the major heterotrophic bacterial populations isolated from a still bottled mineral water

The heterotrophic bacterial population of a bottled mineral water stored in returnable glass bottles and in polyvinyl chloride (PVC) bottles at room temperature was studied over 9-12 months. The plate counts in R2A medium incubated at 22 degrees and 37 degrees C were low initially, increasing to 10(4)-10(5) cfu/ml within a few days of bottling. The number of bacteria recovered at 22 degrees C from PVC bottles was fairly constant during the storage period, but the population isolated at 37 degrees C decreased markedly after storage for 1 year. The major components of the population were Pseudomonas strains, one of which was identified as Pseudomonas vesicularis. Major changes took place during storage; two groups of bacteria (B and C) were dominant initially, but during the latter period of storage other groups (F, G and H) increased in number.

Monitoring genetically engineered microorganisms in freshwater microcosms

The effectiveness of gene probe methods for tracking genetically engineered microorganisms (GEMs) in the environment was tested by inoculating nutrient-supplemented freshwater microcosms withAlcaligenes A5 (a naturally occurring 4-chlorobiphenyl degrader) orPseudomonas cepacia AC1100 (a genetically engineered 2, 4, 5 T-degrader) and following the fates of the introduced bacterial populations. Colony hybridization of the viable heterotrophic bacterial populations and dot blot hybridization of DNA recovered from the total microcosm microbial communities showed persistence of bothAlcaligenes A5 andP. cepacia AC1100 in the microcosms in the presence and absence of the xenobiotic substrates that these organisms biodegrade. Although there was a gradual decline in the added populations, both of the bacterial populatins were still detected in the microcosms two months after their introduction into the microcosms. Addition of 2, 4, 5-T enhanced the survival ofP. cepacia AC1100 — and 4-chlorobiphenyl addition resulted in increased levels ofAlcaligenes A5. The results indicate that both organisms may persist for very long periods in freshwater habitats.

Use of the thermotolerant Aeromonas group for the trophic state classification of freshwaters

Data obtained from 68 lakes surveyed in the United States showed a highly significant correlation between the densities of a specific group of autochthonous, heterotrophic bacteria, thermotolerant aeromonads and the trophic state of fresh waters. This measurement provides a sensitive, accurate and facile descriptor of limnetic water quality and shows strong correlations with certain other commonly employed physical, chemical and biological parameters used in this regard. The best correlations were obtained with Secchi depth ( r = −0.70 ), total phosphorus ( r = 0.72 ) and chlorophyll α ( r = 0.67 ). An even stronger correlation was obtained with a trophic index derived from these three parameters ( r = −0.84 ). Alternatively, total heterotrophic bacterial populations, as enumerated by epifluorescence microscopy, were very poorly correlated with all the individual trophic state measurements, and the indices derived from them. An analysis of correlation coefficients for trophic state parameters and indices used for this study indicated that the level of thermotolerant aeromonads was one of the most discriminating single parameters for defining trophic state. The economy of the measurement, coupled with its facility, makes it an exceptionally promising technique for assessing the degree and rate of fresh water eutrophication.

Bacteriological and chemical studies of wastewater from a chemical fertilizer plant

During 1984 and 1985, a physicochemical analysis of the wastewaters from the nitrate fertilizer industry in the Aswan area was carried out. Heterotrophic bacterial populations, which developed during the journey of the wastewater in the Kima canal before it joined with the River Nile, were investigated. The principal wastewater parameters which deviate significantly from set standards were: NO 3 −, NO 2 −, SO 4, Cl, TA, COD and free NH 3. Mesophilic and heterotrophic populations (12 × 10 2 ml −1) exceeded thermophilic ones (3 × 10 2 ml −1); psycrophilic ones were not observed. Gram-negative rods, spore-formers, nitrate-reducers, catalase-positive organisms and non-producers of H 2S and indole were the predominant types. As they have a high biochemical activity, the biological indices of the wasterwater changes were explained.

The use of R2A medium and the spread plate method for the enumeration of heterotrophic bacteria in drinking water

The pour plate method with yeast extract agar and a 3 d incubation period is the standard method in the UK for the enumeration of heterotrophic bacteria in drinking water. We have compared the standard method with other procedures using the spread plate technique, R2A medium and a longer incubation period. The R2A spread plate method with a 7 d incubation period gave an average estimate of bacterial numbers 520 times greater than for the standard method. This alternative method is recommended for obtaining a more accurate estimate of heterotrophic bacterial populations in drinking water.

Bacterial flora of healthy and abnormal chaetognaths.

Freshly captured chaetognath Sagitta samples were grouped into apparently healthy and abnormal specimens and the viable heterotrophic bacterial population of both groups were ex-amined. The bacterial population ranged from 1.3×102 to 1.0×104 per animal, and was one order higher in opaque specimens regardless of whether they were still moving or moribund at the time of capture. Although Pseudomonas-Alteromonas was the predominant bacteria in both groups, Vibrio comprised 36.3%, of the bacterial population in the abnormal Sagitta. By the method of numerical taxonomy the total 143 strains were grouped into 14 main phena, of which 4 were exclusively composed of strains from healthy Sagitta and 1 from abnormal Sagitta. The rest of the strains were unevenly distributed into 9 phena, 4 of which were mostly comprised of strains from abnormal Sagitta and 1 of which mostly included strains from healthy Sagitta. In general, the isolates of abnormal Sagitta grew under a wide range of physiological conditions and showed greater hydrolytic activities of organic compounds.

Factors Determining Algal Populations in Waste Stabilization Ponds and the Influence of Algae on Pond Performance

In situ and laboratory experiments were performed on species of the waste stabilization pond algae Chlorella, Scenedesmus, Euglena and Chlamydomonas to investigate the utilization of various organic acids and sugars, light limitation on species dominance and the toxicity of ammonia and sulphide. Euglena showed the most flexible metabolism and was able to utilise butyrate. Scenedesmus did not grow on any of the substrates in the dark. Pond populations of Euglena and Chlamydomonas were able to incorporate acetate in situ in competition with the heterotrophic bacterial population but Chlamydomonas was the more successful. Light availability affected speciation in facultative ponds where rapid motility by flagellates was a clear advantage. All the algal species were sensitive to sulphide at µM concentrations in a tolerance sequence ChlamydomonasChlorellaScenedesmusEuglena. Ammonia was less toxic than sulphide and the tolerance sequence was ChlorellaScenedesmusChlamydomonasEuglena. It was the undissociated forms of both sulphide and ammonia which were toxic, Toxicity was influenced by pH and this would be a critical factor controlling ammonia inhibition of algal photosynthesis in ponds. The effects of these findings are related to species dominance and pond performance.

An annual cycle of abundance and activity of heterotrophic bacteria and abundance of hydrocarbonoclastic bacteria in Newfoundland coastal water

An annual cycle of abundance and activity was determined for bacteria in Newfoundland coastal water that is dominated by the Labrador Current. Both in abundance and activity, the population showed characteristics similar to those reported for bacteria in cold ocean environments. The number of bacteria per litre determined by the acridine orange direct count method ranged from an average low of 0.25 × 108 in winter to an average high of 2.8 × 108 in summer. Activity, determined by the kinetic method, was correlated with temperature. The average heterotrophic potential (Vmax) was 3 ng glutamate. L−1∙h−1 in winter and 54.7 ng glutamate. L−1∙h−1 in summer. The average turnover times were 2632 and 256 h, respectively, during the same periods. The population of hydrocarbonoclastic bacteria, estimated by a most probable number method, constituted 4.4% of the viable bacterial population estimated by the standard plate count method, although the former were most abundant near the water's surface. The number of hydrocarbonoclastic bacteria was correlated with temperature and with Vmax of the heterotrophic bacterial population.

Growth of bacteria in an oil shale retort water by indigenous microorganisms.

Previous studies have shown that relatively high aerobic and anaerobic (or facultatively anaerobic) heterotrophic bacterial population densities occur as indicated by an increase in the turbidity of freshly filtered (0.4 ..mu..m) Omega-9 retort water after a few days incubation at room temperature. Growth of these microorganisms alters the nature and concentrations of dissolved organic and inorganic constituents. Bacteria are the only microorganisms known to have demonstrated a capacity to grow in undiluted Omega-9 retort water. Bacterial growth experiments are performed for a variety of reasons. In some situations microorganisms are cultivated to yield a specific product, as a protein source, or because their growth in a particular medium removes certain undesired constituents. Nutritional and physical parameters will often govern the rate at which growing microbial populations proliferate. It was considered important, therefore, to establish what rates of bacterial growth were occurring in the Omega-9 retort water by indigenous, mixed bacterial populations. The study reported here was devised to assess bacterial growth characteristics in an example retort water. Information of this type may have implications in 1) the development of biological treatment systems, 2) establishing hazard assessment and abatement criteria, and 3) in assessing the stability of research samples.