Effects of community composition and growth rate on aquifer biofilm bacteria and their susceptibility to betadine disinfection

Biofilm formation and function was studied in mixed culture using 20 bacterial strains isolated from a karst aquifer. When co-cultured in a glucose-limited chemostat, Vogesella indigofera and Pseudomonas putida were the dominant planktonic and biofilm organisms respectively. Biofilm formation and resistance to the iodine disinfectant betadine were then studied with monoculture and binary cultures of V. indigofera and P. putida and a 20-strain community. Biofilm population size [measured as colony-forming units (CFU) cm⁻²] increased with increasing species diversity. Significantly larger populations formed at dilution rates (DRs) of 0.0083 h⁻¹ than at 0.033 h⁻¹. P. putida populations were higher and V. indigofera lower in binary than in monoculture biofilms, suggesting that P. putida outcompeted V. indigofera . In binary biofilms, V. indigofera , a betadine-resistant organism, enhanced the survival of P. putida , a betadine-susceptible organism. In the 20-strain biofilms, this protective effect was not observed because of low concentrations of V. indigofera (< 1% of the total population), suggesting that resistant organisms contribute to overall biofilm disinfectant resistance. Growth at 0.033 h⁻¹ enhanced survival of V. indigofera biofilms against betadine. Although DR did influence survival of the other communities, its effects were neither consistent nor significant. All told, biofilm formation and betadine resistance are complex phenomena, influenced by community composition, growth rate and betadine concentration.     

Bacterivory by starved marine heterotrophic nanoflagellates of two species which feed differently, estimated by uptake of dual radioactive-labelled bacteria

Abstract: The rates of ingestion of bacteria and of accumulation of bacterial biomass by hungry Pteridomonas danica and Paraphysomonas imperforata were measured using dual radioactive-labelled bacteria in experiments lasting 4–8 h. Pteridomonas continuously consumed 4–5 bacteria h⁻¹ throughout experiments lasting 8 h, irrespective of bacterial concentration above a threshold of about 5 × 10⁵ bacteria ml⁻¹, and continued to catch bacteria even below this density. The clearance rate of about 1 nl cell⁻¹ h⁻¹ at higher bacterial concentrations increased three or four times as bacterial numbers fell. Paraphysomonas cells, with only half the biomass of Pteridomonas , ingested up to 10 bacteria h⁻¹ at high bacterial concentrations, and gradually reduced the feeding rate, effectively ceasing to feed at 10⁶ bacteria ml⁻¹; their initial clearance rate of 1–2.5 nl cell⁻¹ h⁻¹ subsequently fell as low as 0.1 nl cell⁻¹ h⁻¹. Estimation of feeding rate by extrapolation from short-term experiments on such flagellates requires extreme caution. These flagellates, starved to levels typical of the natural environment, accumulated ingested bacterial biomass at an efficiency of between 16 and 21%, indicating that in nature they would recycle 80% or more of the nutrients contained in their food.     

Generation of a reproducible nutrient-depleted biofilm of Escherichia coli and Burkholderia cepacia

An in vitro method of growing bacteria as a defined nutrient-depleted biofilm is proposed. The medium was defined nutritionally in terms of the quantitative composition and by the total amount of nutrient required to achieve a defined population size. Escherichia coli and Burkholderia cepacia were incubated on a filter support placed on a defined volume of solid medium. The change of biomass of the biofilm population was compared with the change in a planktonic culture. The size of the population in stationary phase was proportional to the concentration of limiting substrate up to 40 μmol cm⁻² glucose for E. coli and up to 2·7 × 10⁻⁹ mol cm⁻² iron for B. cepacia . Escherichia coli growing exponentially had a growth rate of μ = 0·30 h⁻¹ in a biofilm and μ = 0·96 h⁻¹ in planktonic culture. The growth rate, μ, for exponentially growing B. cepacia in a biofilm was 1·12 h⁻¹ and in planktonic culture 0·78 h⁻¹. This method allows the limitation of the size of a biofilm population to a chosen value.     

Kinetics of photoautotrophic growth of Marchantia polymorpha cells in suspension culture

Chlorophyllous, cultured cells of Marchantia polymorpha L. (HYA-2 cell line) grow actively under photoautotrophic (lithotrophic) conditions. The maximum specific growth rate (μ_cell) was 0.64 day⁻¹ and the doubling time was 1.08 days under optimum conditions (165 μmol m⁻² s⁻¹, 1% carbon dioxide enriched atmosphere, 25^°C). The photosynthetic activity was 1.30 μmol CO₂-fixed (10⁶ cells)⁻¹ h⁻¹ [66 μmol (mg chlorophyll)⁻¹ h⁻¹] in the exponential phase. The growth course has two distinct phases, an exponential and a linear one. The exponential phase is observed as long as the population density is sufficiently low (less than 7.9 × 10⁶ cells ml⁻¹), so that practically all individual cells directly receive the full incident light. The effect of light on the specific growth rate is a linear function of photon flux density. Linear growth occurs after the population density is so high that the incident light is almost completely absorbed by the cell suspension. The growth rate is a logarithmic function of photon flux density, in contrast to the specific growth rate, and saturates at high photon flux densities. The conditions of maximum growth, however, are not wellbalanced between cell mass production and cell division. Therefore, the maximum growth does not continue for a long time.     

Lactic acid production by Lactobacillus delbrueckii in a dual reactor system using packed bed biofilm reactor

Aims:  An integrated dual reactor system for continuous production of lactic acid by Lactobacillus delbrueckii using biofilms developed on reticulated polyurethane foam (PUF) is demonstrated.
Methods and Results:  Lactobacillus delbrueckii was immobilized on PUF, packed in a bioreactor and used in lactic acid fermentation. The rate of lactic acid production was significantly high with a volumetric productivity of 5 g l⁻¹ h⁻¹ over extended period of time. When coupled to a bioreactor, the system could be operated as dual reactor for over 1000 h continuously without augmentation of inoculum and no compromise on productivity.
Conclusions:  Polyurethane foams offer an excellent support for biofilm formation.
Significance and Impact of the Study:  The system was very robust and could be operated for prolonged period at a volumetric productivity of 4–6 g l⁻¹ h⁻¹.     

Photosynthesis and photoassimilation of glucose during photomixotrophic growth of Marchantia polymorpha cells in suspension culture

Even in the presence of glucose the growth of Marchantia polymorpha L. (cell line HYH-2F) requires light, and growth is more sensitive to 10⁻⁶ M 3-(3, 4-dichlorophenyl)-1, 1-dimethylurea than to 10⁻⁴ Antimycin A. The inability of the cells to grow in the dark is due to the low level of respiration. The respiration rate under light increased to four times the dark value. The values of the compensation ratio (the photosyntehtic rate/the respiration rate) for the oxygen exchange were below 1.0 daring the growth period, although oxygen evolution was found. At the early exponential phase, oxygen evolution was 0.373 μmol (mg cell dry weight)⁻¹ h⁻¹ [61.7 μmol (mg chlorophyll)⁻¹ h⁻¹]. M. polymorpha cells are unable to grow anaerobically in the light without a supply of carbon dioxide. When 1% carbon dioxide in nitrogen is supplied, photochemically produced oxygen and energy are sufficient for sustained growth although at significantly reduced yields in both cell dry weight and chlorophyll. Photosyntehtic CO₂ assimilation rate was 0.13 μmol (mg cell dry weight)⁻¹ h⁻¹[11.3 μmol (mg chlorophyll)⁻¹ h⁻¹]. At least one-third of the carbon atoms in cellular constituents seem to be derived from atmospheric carbon dioxide, which indicates that M. polymorpha cells grow photomixotrophicaily.     

The formation of migratory ripples in a mixed species bacterial biofilm growing in turbulent flow

Mixed-species biofilms, consisting of Klebsiella pneumoniae , Pseudomonas aeruginosa , Pseudomonas fluorescens and Stenotrophomonas maltophilia , were grown in glass flow cells under either laminar or turbulent flow. The biofilms grown in laminar flow consisted of roughly circular-shaped microcolonies separated by water channels. In contrast, biofilm microcolonies grown in turbulent flow were elongated in the downstream direction, forming filamentous 'streamers'. Moreover, biofilms growing in turbulent flow developed extensive patches of ripple-like structures between 9 and 13 days of growth. Using time-lapse microscopic imaging, we discovered that the biofilm ripples migrated downstream. The morphology and the migration velocity of the ripples varied with short-term changes in the bulk liquid flow velocity. The ripples had a maximum migration velocity of 800 μm h⁻¹ (2.2 × 10⁻⁷ m s⁻¹) when the liquid flow velocity was 0.5 m s⁻¹ (Reynolds number = 1800). This work challenges the commonly held assumption that biofilm structures remain at the same location on a surface until they eventually detach.     

A new type of metabolism chamber for the determination of active and postprandial metabolism offish, and consideration of results for coregonid and salmon juveniles

The optomotor reaction of juvenile Coregonus schinzipalea Val. et Cuv. and Salmo salar L. was utilized to develop a circular tube metabolism chamber to measure oxygen consumption and ammonia excretion as a function of swimming speed. The metabolism chamber with a constant water flow assured the maintenance of stable conditions. The unidirectional movement of fish was measured in a circular tube with a single narrowing. The relationships between the swimming speed and oxygen consumption or ammonia excretion described by exponential equations allowed the extrapolation towards the standard metabolism, i.e., zero swimming speed. For a juvenile coregonid (0.1–0.15 g individual weight, 2.6–2.8 cm total length) standard metabolism at 14° C was estimated as 0.65 mg0₂ g⁻¹ h⁻¹ and 17.3 μg N(NH₃)g⁻¹ h⁻¹, whereas for juvenile salmon (136mg individual weight) respective values at 22° C were 0.047mg0₂g⁻¹h⁻¹ and 0.61 μg N(NH₃)g⁻¹ h⁻¹. The feeding test with juvenile salmon was also performed in this circular chamber, and in both energy and nitrogen budgets after a meal the partitioning could be precisely attributed to standard metabolism, active metabolism and specific dynamic action (in the case of oxygen consumption) or postprandial nitrogen increase.
The new metabolism chamber allowed the relationship between metabolism and swimming velocity of juvenile fish with developed rheotactic response. It could be used with adult fish for similar purposes.     

Kinetic Measurements of the Turnover Rates of Phenylethylamine and Tryptamine In Vivo in the Rat Brain

Abstract: The turnover rates of phenylethylamine and tryptamine have been estimated as their rates of accumulation after inhibition of monoamine oxidase by pargyline and were found to be 1.53 nmol/g/h and 0.24 nmol/g/h, respectively. Rate constants for the substrate activities of these amines towards monoamine oxidase were calculated as 100 h⁻¹ and 150 h⁻¹, respectively. Tryptamine was found to exhibit a biphasic response to increasing pargyline dosage, demonstrating its dual activity to type B and type A monoamine oxidase, for which two rate constants were obtained, k_B=100 h⁻¹ and k_A=50 h⁻¹.     

Fed-batch culture of Candida guilliermondii FTI 20037 for xylitol production from sugar cane bagasse hydrolysate

A fed-batch culture system was used to study xylitol production by Candida guilliermondii FTI 20037 in a synthetic and a sugar cane bagasse hydrolysate medium. The values achieved for xylitol yield and volumetric productivity were, respectively, 0 · 84 g g⁻¹ and 0 · 64 g l⁻¹ h⁻¹ using the synthetic medium and 0 · 78 g g⁻¹ and 0 · 62 g l⁻¹ h⁻¹ using the hydrolysate medium.     

Survey of wound-induced ethylene production by excised root segments

Ethylene production was measured from excised 10-mm apical and subapical root segments from 50 cultivars in 19 species of 7 families. Monocotyledonous species tended to have much lower rates of ethylene production than dicotyledonous species. Ethylene production was generally higher in apical root segments than in subapical segments within 1 h of wounding. However, cultivars of Cucumis melo , C. sativus , Helianthus annuus , Hibiscus esculentus , and Zea mays had higher rates of ethylene production from subapical segments. In apical root segments, Phaseolus aureus cv. Berken had the highest ethylene production rate (76.7 ηl g⁻¹ h⁻¹), while Zea mays cv. Silver Queen had the lowest rate (0.6 ηl g⁻¹ h⁻¹). In subapical root segments, Cucumis sativus cv. Armenian had the highest rate (55.7 ηl g⁻¹ h⁻¹), while Zea mays cv. Silver Queen again had the lowest rate (0.6 ηl g⁻¹ h⁻¹). The many different responses in magnitude and kinetics of wound-induced ethylene production among the species, cultivars and tissues should provide interesting and useful systems with which to study wound responses and induced ethylene production.     

Simultaneous phototrophic and chemotrophic growth in the purple sulfur bacterium Thiocapsa roseopersicina M1

Abstract The anoxygenic phototrophic purple sulfur bacterium Thiocapsa roseopersicina was grown in illuminated continuous cultures with thiosulfate as growth limiting substrate. Aeration resulted in completely colorless cells growing chemotrophically, whereafter the conditions were changed to a 23 h oxic/1 h anoxic regime. After 11 volume changes at a dilution rate of 0.031 h⁻¹ (35% of μ_max) a time dependent equilibrium was established. During the 23 h oxic periods bacteriochlorophyll a synthesis (BChl a ) was not observed, whereas during the 1 h anoxic periods synthesis was maximal (i.e. 1.1 μg (mg protein)⁻¹ h⁻¹). As a result the BChl a concentration gradually increased from zero to an average value over 24 h of 1.9 μg (mg protein)⁻¹. Concomitantly, the protein concentration increased from 13.9 mg 1⁻¹ during continuous oxic conditions to 28.8 mg 1⁻¹. For comparison, the protein concentration during fully phototrophic growth at an identical thiosulfate concentration in the inflowing medium was 53.7 mg 1⁻¹. The specific respiration rate was 8 μmol O₂ (mg protein)⁻¹ h⁻¹ during full chemotrophic growth and gradually decreased to 3.5 μmol O₂ (mg protein)⁻¹ h⁻¹ after 11 volume changes at the regime employed. These data show that T. rosepersicina is able to simultaneously utilize light and aerobic respiration of thiosulfate as sources of energy. The ecological relevance of the data is discussed.     

An external heat pulse method for measurement of sap flow through fruit pedicels, leaf petioles and other small-diameter stems

The external heat ratio method is described for measurement of low rates of sap flow in both directions through stems and other plant organs, including fruit pedicels, with diameters up to 5 mm and flows less than 2 g h⁻¹. Calibration was empirical, with heat pulse velocity ( v _h) compared to gravimetric measurements of sap flow. In the four stem types tested ( Actinidia sp. fruit pedicels, Schefflera arboricola petioles, Pittosporum crassifolium stems and Fagus sylvatica stems), v _h was linearly correlated with sap velocity ( v _s) up to a v _s of approximately 0.007 cm s⁻¹, equivalent to a flow of 1.8 g h⁻¹ through a 3-mm-diameter stem. Minimum detectable v _s was approximately 0.0001 cm s⁻¹, equivalent to 0.025 g h⁻¹ through a 3-mm-diameter stem. Sensitivity increased with bark removal. Girdling had no effect on short-term measurements of in vivo sap flow, suggesting that phloem flows were too low to be separated from xylem flows. Fluctuating ambient temperatures increased variability in outdoor sap flow measurements. However, a consistent diurnal time-course of fruit pedicel sap flow was obtained, with flows towards 75-day-old kiwifruit lagging behind evaporative demand and peaking at 0.3 g h⁻¹ in the late afternoon.     

On the diel rhythms in metabolism and activity of post-hatching lesser spotted dogfish, Scyliorhinus canicula

The diel rhythms in metabolic rate ( M_R ) and activity level ( A_L ) were measured for single post-hatching dogfish (weight range, 2.76–10.61 g) at 15° C by the indirect calorimetric method of rate of oxygen consumption ( V O₂) and by video-observation respectively, over a period of 72 b. The mean VO ₂ increased from 62.0 (s.e. 2.9) mg O₂ kg⁻¹ h⁻¹ in the daylight hours to 85.5 (s.e. 3.1) mg O₂ kg⁻¹ h⁻¹ during the dark (light regíme, 12 h L: 12 h D). The simultaneous measurement of A _L also showed mean night elevation from 0.6 (s.e. 0.2) min h⁻¹ in the light phase to 14.5 (s.e. 1.6) min h⁻¹ during the darkness. Bimodal nocturnal activity (BNA) was exhibited by the post-hatching dogfish within the 12 h dark period, with V O₂ increasing from 71.4 (s.e. 2.8) mg O₂ kg⁻¹ h⁻¹ before 01.00 hours to 99.5 (s.e. 4.2) mg O₂ kg⁻¹ h⁻¹ after 01.00 hours. Similarly, A _L also increased from 8.9 (s.e. I.7)min h⁻¹ before 01.00 hours to 21.1 (s.e. 2.8) min h⁻¹ after 01.00 hours. The importance of the results presented to the natural behavioural ecology of the hatching dogfish are discussed.     

Acid phosphatase production by Aspergillus niger N402A in continuous flow culture

The production of acid phosphatases (E.C.3.1.3.2, ACPs) by Aspergillus niger N402A is regulated by specific growth rate, as well as phosphate availability and pH, as demonstrated by studies in continuous flow culture. Specific ACP activity was highest when A. niger was grown at pH 6.3 (64±8 U g⁻¹) or pH 2.8 (99±11 U g⁻¹), at a dilution rate of 0.07 h⁻¹ and phosphate concentrations below 0.46 mM. ACP production was growth correlated for specific growth rates between 0.07 and 0.13 h⁻¹. Four different ACPs, including two phytases, were produced by A. niger N402A. The ACP and the phytase with maximal activities at pH 5.5 were differentially expressed at different culture pH values, with greater production at low pH.     

Anaerobic oxidation of dimethylsulfide and methanethiol in mangrove sediments is dominated by sulfate-reducing bacteria

The oxidation of dimethylsulfide and methanethiol by sulfate-reducing bacteria (SRB) was investigated in Tanzanian mangrove sediments. The rate of dimethylsulfide and methanethiol accumulation in nonamended sediment slurry (control) incubations was very low while in the presence of the inhibitors tungstate and bromoethanesulfonic acid (BES), the accumulation rates ranged from 0.02–0.34 to 0.2–0.4 nmol g FW sediment⁻¹ h⁻¹, respectively. Degradation rates of methanethiol and dimethylsulfide added were 2–10-fold higher. These results point to a balance of production and degradation. Degradation was inhibited much stronger by tungstate than by BES, which implied that SRB were more important. In addition, a new species of SRB, designated strain SD1, was isolated. The isolate was a short rod able to utilize a narrow range of substrates including dimethylsulfide, methanethiol, pyruvate and butyrate. Strain SD1 oxidized dimethylsulfide and methanethiol to carbon dioxide and hydrogen sulfide with sulfate as the electron acceptor and exhibited a low specific growth rate of 0.010 ± 0.002 h⁻¹, but a high affinity for its substrates. The isolated microorganism could be placed in the genus Desulfosarcina (the most closely related cultured species was Desulfosarcina variabilis , 97% identity). Strain SD1 represents a member of the dimethylsulfide/methanethiol-consuming SRB population in mangrove sediments.     

Continuous deacidification of wine by immobilized Schizosaccharomyces pombe cells: evaluation of malic acid degradation rate and analytical profiles

Schizosaccharomyces pombe cells entrapped in Ca alginate gel were used under continuous fermentation conditions to evaluate the extent of malic acid degradation at different dilution rates ( D , h⁻¹) and the analytical profiles of wines obtained. Gel entrapped cells caused the deacidification of wine without affecting the analytical profiles. Maximum deacidification rate was obtained at 0.076 h⁻¹ D while higher dilution rates (up to 0.100 h⁻¹ D ) resulted in a clear reduction of activity. At D -value of 0.055 h⁻¹, the deacidification activity remained constant during the observation period of 360 h.     

Ammonium ion affecting tylosin production by Streptomyces fradiae NRRL 2702 in continuous culture

Nitrogen regulation in tylosin production by Streptomyces fradiae NRRL 2702 was studied in chemostat culture using a soluble synthetic medium. The maximum value of specific tylosin formation rate ( q _TYL) was 1·13 mg g⁻¹ h⁻¹ at the specific growth rate (μ) of 0·05 h⁻¹, and q _TYL decreased with increasing levels of the specific growth rate after reaching a rate of 0·1 h⁻¹. The optimum conditions for tylosin formation were that the specific ammonium ion uptake rate ( q _N) and μ were 0·13 mmol g⁻¹ h⁻¹ and 0·05 h⁻¹, respectively. The specific formation rates of threonine dehydratase (TDT) and tylosin were repressed by high levels of specific ammonium ion uptake rate. This study showed the adaptation to chemostat cultures of the nitrogen regulation of tylosin fermentations.     

Decline of the African lungfish (Protopterus aethiopicus) in Lake Victoria (East Africa)

Catch and effort data for the period 1973–1990 demonstrate a dramatic decline of lungfish in the Tanzanian waters of Lake Victoria. Bottom trawl catches in the Mwanza Gulf showed a decline in catch rates from 67.5 kg h⁻¹ in 1973 to 5.5 kg h⁻¹ in 1986. Trawling of commercial vessels in the Speke Gulf revealed a decline in lungfish catches from 1.3 kg h⁻¹ in 1986 to 0.07 kg h⁻¹ in 1990. The development of anoxia in the deeper waters of Lake Victoria, the algal blooms, and the decline of water transparency, all associated with eutrophication, are not likely to have contributed to the decreased catch rate. However, the lungfish decline may reflect the interaction of overexploitation by the fishery and a low level of Nile perch predation that restricts lungfish to wetland refugia. We suggest that this may have been reinforced over the past few decades by large-scale conversion of wetlands to agricultural land and harvesting of nest-guarding male lungfish leading to decreased recruitment of young.     

Cultivation of nitrifying bacteria in the retentostat, a simple fermenter with internal biomass retention

Abstract: The retentostat was developed for long-term continuous, axenic cultivation of microorganisms at those low growth rates which prevail in most natural habitats and which cannot be established properly in chemostats. How a microbial population approaches 'zero-growth' was studied in axenic cultures of Nitrosomonas europaea with complete biomass retention at 25°C and constant input of a nutrient solution containing ammonium (0.57 mM) as energy source. Since only cell-free filtrate left the reactor, biomass accumulated until a stable maximum of 2.7 × 10⁹ cells ml⁻¹ (398 mg l⁻¹ dry matter) was reached after about 5 weeks. In this state, growth rate approached zero, and the ammonium input just met the substrate demand required for maintenance energy (1.43 μmol NH₃–N mg dm⁻¹ h⁻¹). The potential of the retentostat for studying interactions between different microorganisms was demonstrated with a cascade of cultures of Nitrosomonas, Nitrobacter , and a denitrifying Pseudomonas . Thereby the ammonia was completely eliminated from artificial wastewater.