The impacts of the AOC concentration on biofilm formation under higher shear force condition

The logistic growth model was applied in the study to evaluate the impacts of assimilable organic carbon (AOC) concentration on the growth characteristics of biofilm and bulk bacteria under high flow velocity condition. The experimental results showed that there existed a growth and decline relation between biofilm and bulk bacteria at the low (0.05 mg/L) and medium (0.5 mg/L) AOC levels. Increasing the AOC concentration up to 1.0 mg/L, it resulted in high amounts of biofilm and bulk bacteria simultaneously. Although the carrying capacity of biofilm bacteria at the medium condition of AOC level was substantially reduced, the specific growth rate (GR) of biofilm bacteria was largest at this condition. It showed that the reduction of biofilm bacteria quantity did not represent the suppression of bacterial growth. The quantity of bulk water bacteria was obviously dependent with the quantity of biofilm bacteria and the increase of free bacteria with time in networks was mainly due to the growth and detachment of biofilm bacteria, not due to the growth of free bacteria themselves. The maximum growth rate of biofilm bacteria was increased upon increasing the AOC level. It indicated that the AOC level was an important factor affecting the growth of biofilm bacteria.     

Growth efficiencies of freshwater bacterioplankton

The growth efficiency of freshwater bacteria was examined in continuous cultures. One series of experiments was carried out using generation times from 50 to 200 hours and aged, normal, and enriched media, all of natural origin. Another series of experiments examined the bacterial growth efficiency during the growth season in eutrophic Frederiksborg Slotssø, in relation to changes in the planktonic communities and to factors controlling the bacterial incorporation of ³H-thymidine. Attachment of bacteria to the inner surfaces of the experimental flasks was examined using various types of bottles, adding glass tubes to the bottles, and measuring ³H-thymidine incorporation and direct cell counts of attached and free-living bacteria. Attachment of bacteria varied, and in one example up to 36% of the thymidine incorporation was by attached bacteria after 4 days. It was calculated that 36% of attached bacteria caused an underestimation of the growth efficiency of 11%. The mean growth efficiency tended to decrease with generation time using enriched medium (47 to 19%) and aged medium (35 to 12%), and tended to decrease with medium quality (enriched > normal > aged media) from 37% to 27%. The only significant difference in growth efficiency occurred in relation to generation time, in samples with enriched medium (unpaired t-test, P < 0.05). The overall mean value for all generation times and media was 30% (SEM = 3%, n = 24). From April to October, the growth efficiency was determined 5 times in samples from Frederiksborg Slotssø. The overall mean value was 31% (SEM = 3%, n = 30), and there was no significant change in the growth efficiency during the period measured. In June, three bioassay experiments revealed that carbon limitation controlled bacterial incorporation of ³H-thymidine, whereas additions of phosphate and nitrate did not change the incorporation rates. The narrow range of growth efficiencies obtained in this study (mean 31%, SEM = 2%, n = 54) suggests that changes in substratequality in the media applied and in the eutrophic samples examined causes only subtle changes in the growth efficiency.     

Effects of gold(I) antiarthritic drugs and related compounds on Pseudomonas putida.

The effects of the antiarthritic drugs aurothiomalate (AuTm), aurothioglucose (AuTg), auranofin, its metabolite triethylphosphinegold(I)thioglucose (Et3PAuTg), and several related complexes on the growth of Pseudomonas putida were studied. Two strains were used, one of which (BK135) was more sensitive to Et3PAuTg (tolerant up to 4 microM) than the other (BK403; tolerant to at least 500 microM). Gold thiolate complexes and thiolate ligands alone had little effect on growth. Gold phosphine complexes increased the length of the lag phase of growth and reduced oxygen uptake. Marked changes in cellular morphology were determined by electron microscopy. Copper(II) compounds and aurothiomalate were synergistic in their growth inhibitory effects towards these bacteria. Experiments with 195Au suggested that a mechanism does not exist for the short term (minutes) uptake of gold by sensitive or resistant bacteria, but the resistant strain appeared to limit gold uptake over a longer term (hours).     

猴头菇抽提物对乳酸菌生长的影响

猴头菇抽提物对乳酸菌生长的影响进行了研究,结果表明：猴头菇抽提物对乳酸菌的生长具有促进作用,即使猴头菇抽提物的添加量达到10％,也不会对乳酸菌的生长产生抑制作用。在离体条件下,猴头菇抽提物对双歧杆菌的促生长效果明显优于低聚异麦芽糖和低聚果糖等双歧因子,在TPY液体培养基中添加2％的猴头菇抽提物可以使双歧杆菌活菌数从108个／ml提高到109个／ml。     

Comparison of the Growth and Survival of Larval Turbot in the Absence of Culturable Bacteria with Those in the Presence of Vibrio anguillarum, Vibrio alginolyticus, or a Marine Aeromonas sp

Larval turbot (Scophthalmus maximus) were reared on rotifers (Brachionus plicatilis) in the absence of culturable bacteria for up to 14 days and exhibited growth and high rates of survival (>55% in five experiments). Low numbers of known bacteria were introduced into similar cultures by exposure of the rotifers to a suspension of bacteria prior to addition of rotifers to the larval cultures; Vibrio anguillarum 91079 caused a highly significant decrease (P <0.01) in the proportion of survivors in two separate trials. With an Aeromonas sp. previously isolated from a healthy batch of copepod-fed larvae, there was no significant difference in survival compared with control larvae, even though the density of bacteria in the water of larval cultures reached 10(sup7) ml(sup-1). Bacteria colonized the gut of larvae exposed to Aeromonas-treated rotifers to levels similar to those in conventionally reared fish (>4 x 10(sup4) CFU per larva). Rearing of larvae in the presence of known bacteria provides a means of investigating the interaction of specific bacteria with turbot larvae and could provide a method for the selection of bacteria which may restrict the growth of opportunistic pathogens which would be harmful to turbot larvae.     

Gaseous CO2 signal initiates growth of butyric-acid-producing Clostridium butyricum in both pure culture and mixed cultures with Lactobacillus brevis

Microbial strains produce numerous volatile substances in the anaerobic conditions of the human intestines. The availability of CO(2) is known to be a prerequisite for bacterial growth in general. In experiments with anaerobic Lactobacillus brevis and Clostridium butyricum bacteria in the Portable Microbial Enrichment Unit (PMEU) it was shown that these strains interact; this interaction being mediated by CO(2) emission. CO(2) promoted clostridial growth in pure cultures and mixed cultures with lactobacilli. The growth of C. butyricum in pure cultures was much delayed or did not start at all without CO(2) from outside. Conversely, the onset of growth was provoked by a short (15 min) CO(2) burst. In mixed cultures the presence of lactobacilli in equal numbers speeded up the onset of clostridial growth by 10 h. If C. butyricum cultures designated as PMEU 1, 2, and 3 in cultivation syringes were chained by connecting the gas flow thereby allowing the volatiles of the preceding syringe culture to bubble to the next one, the growth started in 20, 10, or 6 h, respectively. This effect of gaseous emissions from other cultures speeding up the bacterial growth initiation was abolished if the gas was passed through sodium hydroxide to remove the CO(2). The positive contribution of lactobacilli to the growth of butyric-acid-producing clostridia documented in this simulation experiment with PMEU has in vivo implications and indicates molecular communication between the species. CO(2) is a necessary signal for the growth of clostridia, and lactobacilli can promote clostridial growth in mixed cultures where both bacteria grow well with mutual benefit.     

Growth behaviour and indole acetic acid (IAA) production by a Rhizobium isolated from root nodules of Alysicarpus vaginalis DC

From the root nodules of Alysicarpus vaginalis DC, the symbiont was isolated and identified as a Rhizobium sp. The bacteria produced a high amount (107 microg/ml) of indole acetic acid (IAA) in culture from tryptophan supplemented yeast extract mannitol medium. The isolate preferred L-isomer of tryptophan for maximum IAA production. The production was maximum when the bacteria reached its stationary phase of growth. The production of IAA could be increased up to 70% over yeast extract glucose medium by supplementing ZnSO4, 7H2O (0.5 microg/ml). L-asparagine (0.2%) and sodium dodecyl sulfate (1.0 microg/ml). The possible relationship between the rhizobial IAA production and legume-rhizobia symbiosis is discussed.     

有机物料厌氧发酵液中拮抗苹果再植障碍病原真菌的细菌筛选及其防治效果

有机物料厌氧发酵液(AFOF)能显著改善苹果再植障碍.本研究对AFOF中能拮抗苹果再植障碍主要病原菌(腐皮镰刀菌、层出镰刀菌、尖孢镰刀菌、串珠镰刀菌)的细菌进行了分离筛选,并对其作用效果进行了盆栽验证.结果表明: AFOF能显著抑制病原真菌的生长繁殖;对峙试验共得到4株具有较强拮抗作用的细菌(L11、L12、L13、L14),最高抑菌率达到57.3%,鉴定发现这4株细菌均属于芽孢杆菌属,相互之间没有明显的拮抗作用;在盆栽条件下,与连作土相比,溴甲烷熏蒸处理和拮抗菌菌液处理对平邑甜茶幼苗的生物量均有不同程度的促进作用;在幼苗的长势上,溴甲烷熏蒸处理效果要好于拮抗菌菌液处理;在根系活力上,拮抗菌菌液处理效果要好于溴甲烷熏蒸处理,根系长度、根尖数分别增加了25.1%、70.9%.与连作土处理相比,拮抗菌菌液和溴甲烷熏蒸均能显著降低土壤中的真菌数量,分别降低了71.2%和64.2%,拮抗菌菌液处理能显著增加土壤中的细菌和放线菌数量,分别增加了48.0%和140.2%,使土壤微生物结构向“细菌型”转化;而溴甲烷熏蒸处理显著降低了土壤中的细菌和放线菌数量,说明拮抗菌的确能够抑制土壤中病原真菌的生长.     

Sulfate reduction from phosphogypsum using a mixed culture of sulfate-reducing bacteria

Phosphogypsum (CaSO₄), a primary by-product of phosphoric acid production, is accumulated in large stockpiles and occupies vast areas of land. It poses a severe threat to the quality of water and land in countries producing phosphoric acid. In this study, the potential of sulfate-reducing bacteria for biodegradation of this sulfur-rich industrial solid waste was assessed. The effect of phosphogypsum concentration, carbon and nitrogen sources, temperature, pH and stirring on the growth of sulfate-reducing bacteria was investigated. Growth of sulfate-reducing bacteria was monitored by measuring sulfide production. Phosphogypsum was shown to be a good source of sulfate, albeit that the addition of organic carbon was necessary for bacterial growth. Biogenic sulfide production occurred with phosphogypsum up to a concentration of 40 g L⁻¹, above which no growth of sulfate-reducing bacteria was observed. Optimal growth was obtained at 10 g L⁻¹ phosphogypsum. Both the gas mixture H₂/CO₂ and lactate supported high amounts of H₂S formation (19 and 11 mM, respectively). The best source of nitrogen for sulfate-reducing bacteria was yeast extract, followed by ammonium chloride. The presence of nitrate had an inhibitory effect on the process of sulfate reduction. Stirring the culture at 150 rpm slightly stimulated H₂S formation, probably by improving sulfate solubility.     

Microbial community response to a release of neat ethanol onto residual hydrocarbons in a pilot-scale aquifer tank

The microbial community response to a neat ethanol release (E100, 76 l) onto residual hydrocarbons in sandy soil was evaluated in a continuous-flow 8 m(3) pilot-scale aquifer tank, simulating a release at a bulk fuel terminal. Microbial genotypic shifts were assessed using quantitative real-time PCR analysis. High ethanol concentrations in the capillary fringe at potentially toxic levels, exceeding 100,000 mg l(-1), were tolerated by the microbial community. The high biochemical oxygen demand exerted by ethanol rapidly induced anaerobic conditions, and both methane production (up to 1.2 mg l(-1)) and growth of putative methanogenic Archaea (up to 10(6) gene copies per g of soil) were observed in shallow groundwater and soil samples 75 cm down gradient from the source. Aerobic conditions returned after ethanol was flushed out of the system, approximately 45 days after the spill (less than 7.5 pore volumes flushed). Total Bacteria growth coincided with ethanol migration and availability, which was restricted to a relatively thin layer at the capillary fringe and water table interface. The concentrations of bacteria harbouring the aerobic catabolic genes dmpN (coding for phenol hydroxylase) and to dC1 (coding for toluene dioxygenase) increased (up to 100x) down gradient from the source, likely as a result of both fortuitous growth on ethanol and on aromatic hydrocarbons mobilized by ethanol. Growth of hydrocarbon degraders was corroborated by denaturing gradient gel electrophoresis analysis showing proliferation of Azospirillum and Brevundimonas spp., which are bacteria commonly associated with microaerophilic hydrocarbon degradation. Nevertheless, the relative abundance of hydrocarbon-specific degraders (as a fraction of total Bacteria) decreased as other bacteria grew to a higher extent. Overall, the observed growth of hydrocarbon degraders suggests a potential enhancement in aerobic natural attenuation in shallow aquifers after ethanol and its degradation by-products are degraded or flushed from sites impacted by ethanol-blended fuels.     

Viability and metabolic capability are maintained by Escherichia coli, Pseudomonas aeruginosa, and Streptococcus lactis at very low adenylate energy charge.

Metabolic regulation by nucleotides has been examined in several bacteria within the context of the adenylate energy charge (EC) concept. The ECs of bacteria capable of only fermentative metabolism (Streptococcus lactis and the ATPase-less mutant Escherichia coli AN718) fell to less than 0.2 under carbon-limiting conditions, but the bacteria were able to step up the EC to greater than 0.8 upon exposure to nutrient sugars. Similarly, nongrowing E. coli 25922, whose EC had been artificially lowered to less than 0.1 by the addition of the protonophore carbonyl cyanide m-chlorophenylhydrazone (CCCP), was able to immediately step up the EC to 0.8 to 0.9 upon the addition of glucose but was unable to respond to respiratory substrates. The EC of respiring bacteria (E. coli 25922 and Pseudomonas aeruginosa 27853) fell to 0.3 to 0.4 under certain limiting growth conditions, but the bacteria also responded immediately when challenged with succinate to give EC values greater than 0.8. These bacteria could not step up the EC with respiratory substrates in the presence of CCCP. For all bacteria, the loss of the ability to step up the EC was attributable to the loss of nutrient transport function. Mixtures of viable and HOCl-killed E. coli 25922 were able to step up the EC in proportion to the fraction of surviving cells. The data indicate that nucleotide phosphorylation levels are not regulatory in nongrowing bacteria but that the EC step-up achievable upon nutrient addition may be an accurate index of viability.     

Production and characterization of tannase from Bacillus cereus KBR9

A tannase-producing soil bacteria has been isolated and identified as Bacillus cereus. It can degrade tannic acid and produce maximum tannase (0.22 U/ml) at stationary phases of growth (24 h). Maximum growth and enzyme production occurred with initial medium pH of 4.5-5.0. Partial purified tannase showed optimum activity at pH 4.5 and 40 degrees C. It remains stable up to 30 degrees C and pH 4.5 to 5.0. The enzyme is salt tolerant, stable up to 2 m of NaCl and retains 82% original activity in 3 m.     

Impact of flow velocity on the dynamic behaviour of biofilm bacteria

The impact of flow velocity (FV) on the growth dynamics of biofilms and bulk water heterotrophic plate count (HPC) bacteria in drinking water distribution systems was quantified and modeled by combining a logistic growth model with mass balance equations. The dynamic variations in the specific growth and release rates of biofilm bacteria were also quantified. The experimental results showed that the maximum biofilm biomass did not change when flow velocity was increased from 20 to 40 cm s(-1), but was significantly affected when flow velocity was further increased to 60 cm s(-1). Although the concentration of biofilm bacteria was substantially reduced by the higher shear stress, the concentration of bacteria in the bulk fluid was slightly increased. From this it is estimated that the specific growth rate and specific release rate of biofilm bacteria had doubled. The specific release (detachment) rate was dependent on the specific growth rate of the biofilm bacteria.     

发光酶基因lux AB标记硅酸盐细菌NBT菌株的研究

外源基因标记技术为研究土壤引入细菌的生态行为提供了有效的检测手段,通过选择不同的碳源和降低碳氮比筛选获得0．25％麦芽糖作为碳源的菌体制备培养基,对硅酸盐细菌BT菌株进行紫外诱变和抗生素抗性驯化获得—株抗利福平200μg·ml^-1的NBT-R200菌株,含发光酶基因luxAB的质粒pTR102：：luxAB在辅助质粒pRK2013的帮助下转入该菌株中,从而赋予NBT菌株以发光活性和利福平、卡那霉素、四环素三种抗生素抗性．以对数生长期的菌体制备受体细胞,发现对数生长前期的细胞转移频率最高,可达6．70×10^-5,杂交比例以1：1：1适宜．标记菌株RL85的释钾能力没有丧失且有提高,发光特性稳定,连续转接20次后仍具有发光活性和3种抗生素抗性,适用于根际微生态学研究。     

Protozoan Grazing Increases Mineralization of Naphthalene in Marine Sediment

Bacterial decomposition of organic matter is frequently enhanced when protozoa are present. Various mechanisms have been proposed to account for this phenomenon, including effects associated with grazing by protozoa (such as increased recycling of limiting nutrients, removal of senescent cells, or reduction of competition among bacteria) and indirect effects of grazers (such as excretion of bacterial growth factors). Few studies have examined the role of protozoa in bacterial degradation of xenobiotic compounds in sediment containing a natural community of microbes. The effect of protozoa on mineralization of naphthalene was investigated in this study. Laboratory experiments were conducted using field-contaminated estuarine sediment, with the indigenous microbial populations. Mineralization of naphthalene was up to four times greater in treatments with actively grazing protozoa than in treatments containing the grazing inhibitor cytochalasin B. Control experiments confirmed that the grazing inhibitor was not toxic to ciliates but did prevent them from grazing. The grazing inhibitor did not affect growth rates of a mixed culture of sediment bacteria or a pure polycyclic-aromatic-hydrocarbon-degrading strain. Once grazing had been inhibited, supplementing treatments with inorganic N and P, glucose, or additional protozoa failed to stimulate naphthalene mineralization. Naphthalene-degrading bacteria were four to nine times less abundant when protozoan grazing was suppressed. We suggest that protozoa enhance naphthalene mineralization by selectively grazing on those sediment bacteria that ordinarily would outcompete naphthalene-degrading bacteria.     

Phylloplane bacteria increase seedling emergence, growth and yield of field-grown groundnut (Arachis hypogaea L.)

AIM: To isolate and characterize groundnut-associated bacterial isolates for growth promotion of groundnut in field. METHODS AND RESULTS: Three hundred and ninety-three groundnut-associated bacteria, representing the geocarposphere, phylloplane and rhizosphere, and endophytes were applied as seed treatment in greenhouse. Maximum increase in plant biomass (up to 26%) was observed following treatment with a rhizosphere isolate identified as Bacillus firmis GRS 123, and two phylloplane isolates Bacillus megaterium GPS 55 and Pseudomonas aeruginosa GPS 21. There was no correlation between the production of L-tryptophan-derived auxins and growth promotion by the test isolates. Actively growing cells and peat formulations of GRS 123 and GPS 55, and actively growing cells of GPS 21, significantly increased the plant growth and pod yield (up to 19%) in field. Rifampicin-resistant mutants of GRS 123 and GPS 21 colonized the ecto- and endorhizospheres of groundnut, respectively, up to 100 days after sowing (DAS), whereas GPS 55 was recovered from both the habitats at 100 DAS. CONCLUSION: Seed bacterization with phylloplane isolates promoted groundnut growth indicating the possibility of isolating rhizosphere beneficial bacteria from different habitats. SIGNIFICANCE AND IMPACT OF THE STUDY: Identification of phylloplane bacteria as effective plant growth-promoting rhizobacteria (PGPR) broadens the spectrum of PGPR available for field application.     

Assessment of copper toxicity using an acoustic wave sensor

A piezoelectric quartz crystal microbalance has been shown to be useful to monitor real time bacterial growth. Monitoring bacterial growth can give an insight into the ecosystem, as it is highly affected by the presence of toxic elements or nutrients. The frequency of an uncoated piezoelectric quartz crystal was monitored while in contact with bacteria, isolated from water sampled from a Portuguese lagoon, growing in two different media: a saline nutrient broth (NM) and the natural water. The sensor was used to evaluate the effect of copper on bacterial growth. Copper concentrations up to 18.8 microg l(-1) showed an increase in bacterial growth in NM, and a decrease beyond 25.0 microg l(-1). Copper added to the natural water had negative effects on bacterial growth beyond 18.8 microg l(-1). Copper concentrations in the natural water from the lagoon were determined using a similar quartz crystal to detect the mass deposited by anodic stripping voltammetry, and was found to be 3.38 +/- 0.09 microg l(-1).     

Aerosolization of mycobacteria and legionellae during dental treatment: low exposure despite dental unit contamination

Dental unit waterlines (DUWL) support growth of a dense microbial population that includes pathogens and hypersensitivity-inducing bacteria, such as Legionella spp. and non-tuberculous mycobacteria (NTM). Dynamic dental instruments connected to DUWL generate aerosols in the work environment, which could allow waterborne pathogens to be aerosolized. The use of the real-time quantitative polymerase chain reaction (qPCR) provides a more accurate estimation of exposure levels compared with the traditional culture approach. Bioaerosol sampling was performed 13 times in an isolated dental treatment room according to a standardized protocol that included four dental prophylaxis treatments. Inhalable dust samples were taken at the breathing zone of both the hygienist and patient and outside the treatment room (control). Total bacteria as well as Legionella spp. and NTM were quantified by qPCR in bioaerosol and DUWL water samples. Dental staff and patients are exposed to bacteria generated during dental treatments (up to 4.3 E + 05 bacteria per m(3) of air). Because DUWL water studied was weakly contaminated by Legionella spp. and NTM, their aerosolization during dental treatment was not significant. As a result, infectious and sensitization risks associated with legionellae and NTM should be minimal.     

Influence of glutamate on growth, sporulation, and spore properties of Bacillus cereus ATCC 14579 in defined medium

A chemically defined medium in combination with an airlift fermentor system was used to study the growth and sporulation of Bacillus cereus ATCC 14579. The medium contained six amino acids and lactate as the main carbon sources. The amino acids were depleted during exponential growth, while lactate was metabolized mainly during stationary phase. Two concentrations of glutamate were used: high (20 mM; YLHG) and low (2.5 mM; YLLG). Under both conditions, sporulation was complete and synchronous. Sporulation started and was completed while significant amounts of carbon and nitrogen sources were still present in the medium, indicating that starvation was not the trigger for sporulation. Analysis of amino acids and NH4+ in the culture supernatant showed that most of the nitrogen assimilated by the bacteria was taken up during sporulation. The consumption of glutamate depended on the initial concentration; in YLLG, all of the glutamate was used early during exponential growth, while in YLHG, almost all of the glutamate was used during sporulation. In YLLG, but not in YLHG, NH4+ was taken up by the cells during sporulation. The total amount of nitrogen used by the bacteria in YLLG was less than that used by the bacteria in YLHG, although a significant amount of NH4+ was present in the medium throughout sporulation. Despite these differences, growth and temporal expression of key sigma factors involved in sporulation were parallel, indicating that the genetic time frames of sporulation were similar under both conditions. Nevertheless, in YLHG, dipicolinic acid production started later and the spores were released from the mother cells much later than in YLLG. Notably, spores had a higher heat resistance when obtained after growth in YLHG than when obtained after growth in YLLG, and the spores germinated more rapidly and completely in response to inosine, l-alanine, and a combination of these two germinants.     

耐盐硫氧化菌的筛选、鉴定及脱硫性能研究

【目的】从典型自然环境中筛选耐盐高效硫氧化菌,研究其生长特性,并进行初步脱硫实验。【方法】以硫代硫酸钠为唯一能源底物的培养基富集脱硫菌,经过3次平板划线培养、纯种分离后得到纯种培养。经过革兰氏染色、平板菌落形态观察及形态学特征研究,并结合16S rRNA基因序列分析及分子系统发育树的构建结果,确定菌株的种类。【结果】从上海外高桥某发电厂冷却水池中筛选分离出一株硫代硫酸盐去除率高、耐盐性较强的细菌,命名为CYJN-1。该菌为革兰氏阴性菌,短杆状,鉴定为那不勒斯菌(Halothiobacillus neapolitanus)。H. neapolitanus CYJN-1具有较强适应盐度变化的能力,菌株生长的盐度范围为0?5% (NaCI,质量体积比)。菌株最适生长条件为：温度30 °C、pH 7.0、底物浓度为20 g/L。在此条件下,该菌对硫代硫酸钠的去除率可达98%。【结论】H. neapolitanus CYJN-1耐盐性较强,硫代硫酸盐去除率高,在生物脱硫、生物冶金等领域都具有潜在的应用前景。