A note on the attachment rate of suspended bacteria to submerged aquatic plants in a calcareous stream

The density of epiphytic bacteria on leaflets of laboratory-grown Apium nodiflorum , immersed in calcareous stream water, increased linearly with time over 10 h, both in the laboratory and in the field. This increase was probably due to attachment of suspended bacteria. The rate of attachment to leaflets of plants, immersed in a stream at different concentrations of suspended bacteria, was linearly related to the concentration of suspended bacteria. The attachment rate, relative to concentration, was 1.7 × 10⁴ bacteria/cm²/h for each 10⁵ bacteria/ml in the surrounding water.     

Bacterivory by the ciliate Euplotes in different states of hunger

Abstract: The feeding of the marine ciliate Euplotes mutabilis was studied using bacteria ( Vibrio natriegens ) doubly labelled with ³H-thymidine and ¹⁴C-leucine. In the presence of abundant bacteria (30 × 10⁶ bacteria ml⁻¹), an average Euplotes cell (initially without food vacuoles) with a protein content of 12 ng consumed 16 × 10³ bacteria in the first hour and 27 × 10³ bacteria over four hours, accumulating about 60% of the bacterial protein into ciliate macromolecules. Euplotes which had been starved or under-fed to reduce cell protein biomass to 7 or 9 ng consumed significantly fewer bacteria, but the gross growth efficiency for protein did not change. The rate of consumption of bacteria by large Euplotes of protein content 15 ng was initially less than that of 12 ng cells, and it decreased markedly before the end of a 4-hour experiment. Recently divided cells ingested bacteria rapidly, but showed a reduced gross growth efficiency of about 40%. At low bacterial concentrations (6 × 10⁶ bacteria ml⁻¹) the rates of ingestion were markedly reduced to between     and     of maximal levels; the smallest cells could not sustain feeding activity at the low prey concentration and gross growth efficiency fell from 43 to 20% during a 4-hour experiment. The strategy adopted by Euplotes in response to local fluctuations in food supply involves rapid consumption with high growth efficiency in times of plenty, but slow shrinkage without cell division to survive in times of shortage.     

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.     

The distribution of some freshwater planktonic bacteria in two stratified eutrophic lakes

SUMMARY. Changes in bacterial populations and certain physical and chemical variables in Esthwaite Water between June and September 1975 were studied and compared with results obtained from 1972 to 1974 in the hypolimnia of Blelham Tarn and the Lund tubes. The counts of total bacteria ranged between 1 and 7 × 10⁶ml⁻¹ and were highest in the anoxic hypolimnion. The bacterial genera examined in more detail constituted only a small percentage of this count and included Ochrobium (10⁴ml⁻¹), Naumanniella (10³ml⁻¹), Leptothrix (10²ml⁻¹), Planctomyces (10³ml⁻¹), and Metallogenium (10²ml⁻¹). The iron bacteria appear to grow best in the oxycline where there was not only sufficient oxygen for aerobic growth but also a plentiful supply of reduced iron. Planctomyces numbers increased as the thermocline became depressed in September. The results from Blelham Tarn might be interpreted as further evidence of growth by iron bacteria in the absence of dissolved oxygen, but other explanations are possible. Examination of the results by multiple regression analysis showed that it was possible to explain a significant proportion of the bacterial variation (with the notable exception of the Planctomyces counts) in spite of considerable intercorrelation of the regressor variables.     

Interaction between the effects of bacteria and dry storage on the opening and water relations of cut rose flowers

W.G. VAN DOORN AND K. D'HONT. 1994. Flowering stems of four rose cultivars (Sonia, Madelon, Jacaranda and Frisco) were placed in aqueous suspensions of bacteria at 10⁴ and 10⁸ colony-forming units (cfu) ml^-1 for 24 h at 5C, then stored dry or held in water for 24 h at 8C and subsequently placed in vase-water at 20C. The effects of these treatments on vase-water uptake were similar to the effects on flower opening. In Sonia and Madelon roses flower opening was negatively affected both by 10⁸ cfu ml^-1 of bacteria and by dry storage. No effect was found at 10⁴ cfu ml^-1, but this concentration had a detrimental effect on flower opening when combined with dry storage. Although flower development in Jacaranda roses was not affected by the bacteria treatments it was inhibited by dry storage. This inhibition was progressively greater when the stems had previously been pulse-treated with a larger number of bacteria. Flower opening in Frisco roses was not affected by even the highest concentration of bacteria, nor by the period of dry storage. It is concluded that placing flowers in water containing bacteria (up to 10⁸ cfu ml^-1) may not always have a negative effect on flower development in cut rose flowers but, together with the effects of dry storage, the presence of even a low number of exogenous bacteria (10⁴ cfu ml^-1) inhibits the development in several cultivars. Such bacterial counts are nearly always found in samples of water used for standing roses during distribution to the consumers.     

Bacterial Counts and Quality of Iced Fish Retailed at a Lusaka Market, Zambia

S ummary . The counts of total viable, coliform, streptococcal and sulphite reducing anaerobic bacteria and the presence of salmonellae were determined on 134 iced fish obtained from Luburma Market, Lusaka, Zambia, during June-December 1970. The quality of the uncooked fish was also assessed by appearance and odour. The purpose of these determinations was to obtain a picture of the variations of the bacterial counts in relation to season, origin, fish species and market quality. Total viable and coliform counts were of the order of millions and tens of thousands/cm² of skin surface, respectively. Higher counts were obtained in the hot season during September-October but with little change in appearance of the fish. There was a significant correlation ( P < 0·01) of both total viable and coliform bacteria with quality scores. A maximum permissible level of 10⁷ cells/cm² of skin surface was proposed for total viable counts and 10⁵/cm² for coliform bacteria, for iced fish of acceptable quality in Zambia.     

A Note on the Enumeration of Epiphytic Bacteria by Microscopic Methods with Particular Reference to Two Freshwater Plants

Bacteria on plant surfaces were examined using epifluorescence, bright-field microscopy and an impression technique. Staining bacteria directly on the plant surface with phenolic aniline blue was found to be the best method to use for the determination of bacterial density. The effect on the estimation of population density of pretreatment of the plant with agents such as methanol and eosin yellowish was investigated. The average sizes of the bacterial populations on two freshwater plants, Rorippa and Lemna , estimated after staining by this method, were 5 times 10⁶ and 9 times 10⁶ bacteria cm-^z respectively.     

Binding of vitronectin and plasminogen to Helicobacter pylori

Abstract We have studied how some extracellular matrix proteins, fibronectin, fibrinogen, collagen type I and type IV, plasminogen and vitronectin bind to Helicobacter pylori . Radiolabelled vitronectin and plasminogen bound to the haemagglutinating H. pylori strain 17874 at a high level (53% and 32%, respectively), type IV collagen showed an intermediate level of binding (16%), while binding by ¹²⁵I-labelled fibrinogen, fibronectin and collagen type I remained at a low level (5–7%). Both ¹²⁵I-vitronectin and plasminogen showed a dose-dependent binding to cells of H. pylori 17874. Plasminogen binding by this strain was specific since the binding was inhibited by nonlabelled plasminogen, but not by highly glycosylated glycoproteins such as fetuin and orosomucoid or by a variety of monosaccharides. We have previously shown that ¹²⁵I-vitronectin shows a specific and saturable binding to H. pylori 17874, and that sialic acid-rich glycoproteins such as fetuin and orosomucoid drastically reduced binding. We now report that a simultaneous incubation of ¹²⁵I-vitronectin and ¹²⁵I-plasminogen with cells of H. pylori 17874 showed a total binding approximately similar to the level of binding when either ¹²⁵I-plasminogen, or ¹²⁵I-vitronectin only were incubated with the bacterial cells. Nonlabelled vitronectin inhibited the binding of ¹²⁵I-plasminogen by H. pylori , but nonlabelled plasminogen had no effect on the binding of ¹²⁵I-vitronectin. Our findings suggest that there are different but probably closely localized binding sites for vitronectin and plasminogen on H. pylori 17874.     

Influence of PCBs on the predator-prey relation between bacteria and protozoa in soil

Abstract This work deals with the impact of a possible accidental pollutant, pyralene (Prodelec, France; PCBs in trichlorobenzene), intoduced into the soil. Its influence on the predator-prey relation between bacteria and amoebae was studied by comparing the population dynamics of (i) an inoculated bacterial population ( A. lipoferum ) chosen as a biological tracer, (ii) the indigenous bacterial microflora, (iii) the infigenous amoebae. In the absence of pyralene the inoculated bacterial population decreased from 10⁷ to 10⁴ bacteria g⁻¹ soil (dw), grazed by the infigenous amoebae whose numbers increased 3-fold. In contrast, in presence of 2500 ppm of pyralene the introduced bacteria survived at a higher level (3·10⁶ bacteria g⁻¹ soil (dw)) while the number of amoebae diminished slightly. No predation occurred with PCB contamination. The indigenous bacterial microflora was not affected quantitatively by pyralene. In pure liquid culture with 500 ppm of pyralene added, bacterial growth was inhibited and an amoebal strain isolated from an inoculated uncontaminated soil was killed. We conclude that the active form of the amoebae were killed, and encystement was inhibited by pyralene in the soil. Hence the protozoa were unable to regulate the introduced A. lipoferum strain as they did in the absence of the pollutant.     

The Effects of Insect Juvenile Hormone on the Growth of Some Protozoans in vitro. I. Crithidia sp.

SYNOPSIS. Experiments were designed to investigate the effects of insect juvenile hormone (JH) on the over-all growth and macromolecular synthesis of Crithidia sp. in vitro. Cells grown in the presence of 10⁻⁵M-10⁻³M JH showed a concentration-dependent inhibition of growth, which appeared to result from both a prolongation of generation time and a delay in the onset of logarithmic growth. Juvenile hormone (10⁻³M) inhibited the incorporation of [³H]thymidine, [³H]uridine and [³H] leucine into logarithmically growing cells by 50, 70 and 40% respectively. The incorporation of [³H]uridine into acid insoluble material could be stopped within 1 hr of application of the hormone (10⁻³M). The inhibitory effect was reversible in terms of cell numbers in subcultures of washed cells but an examination of the reversibility of RNA synthesis inhibition suggested that the resumption of RNA synthesis at an optimal level would require a lag period of at least 1–3 hr. It is suggested that JH may act by interfering with RNA synthesis either directly or indirectly by primarily acting at the level of the plasma membrane.     

Binding of collagen to group A, B, C, D and G streptococci

Abstract Binding of ¹²⁵I-labelled collagen type II to group A, B, C, D and G streptococci was studied. Strains of all five serogroups were found to bind. Binding to one high-binding strain (group G, strain 12127) was characterised. This was reversible, saturable with time and inhibited by unlabelled type II collagen, but not by other proteins such as fibronectin and ovalbumin. However, binding was inhibited by unlabelled type I, II and III collagens and gelatin, suggesting that a common structure of various collagens is involved in binding.     

The planktonic and benthic bacterial populations of Lough Neagh

The planktonic and benthic bacterial populations of Lough Neagh, Northern Ireland, were studied over a one-year period. Direct counts of bacteria in the water column averaged 6 times 10⁷/ml with limited spatial or temporal variation; viable counts, however, showed a pronounced late spring maximum of 1.7 times 10⁶/ml and were consistently higher at a littoral sampling station. Direct counts of bacteria in the profundal sediments averaged 8 times 10⁹/ml whilst viable benthic counts rose steeply during spring to reach a June maximum of 1 times 10⁸/ml. Direct: viable count ratios were much greater in the more sandy littoral zone. The predominant benthic isolate was an Aeromonas sp. which was also common in samples from the water column. These results confirm the eutrophic status of Lough Neagh indicated by other biological and chemical surveys.     

Post-processing microflora and the shelf stability of gari marketed in Port Harcourt

Gari was examined for its post-processing microbial content. Aerobic mesophilic bacteria and fungi were isolated from all samples. The total viable bacterial counts ranged from 2.0 × 10² to 8.0 × 10⁴ cfu/g. Fungal counts ranged from 1.0 × 10² to 1.5 × 10⁴ cfu/g. The total viable counts of fresh samples were much lower than those of market and packaged samples. Bacillus, Micrococcus and Proteus spp. were the bacteria isolated, Aspergillus niger, Aspergillus flavus and Penicillium spp. the fungi. Food borne parasites and pathogens such as Staph. aureus and Clostridium perfringens were not found. The gari samples were quite stable, having a shelf life of 3–6 months. The water activities of the samples ranged from 0.52 to 0.68. Based on the microbial counts of the samples, the critical upper limit for the safety of gari was set at 10⁴ cfu/g dry sample.     

Fibronectin binding to a Streptococcus pyogenes strain.

In previous studies, Staphylococcus aureus has been shown to bind fibronectin (P. Kuusela, Nature (London) 276:718-720, 1978), an interaction that may be important in bacterial attachment and opsonization. Recently some strains of streptococci of serological groups A, C, and G were also found to bind fibronectin. The binding to one selected strain of Streptococcus pyogenes has been characterized here. The binding of [125I]fibronectin to streptococcal cells resembles that to staphylococcal cells and was found to be time dependent, functionally irreversible, and specific in the sense that unlabeled proteins other than fibronectin did not block binding. Bacteria incubated with proteases largely lost their ability to bind fibronectin, and material released from the streptococci by a brief trypsin digestion contained active fibronectin receptors. This material inhibited the binding of [125I]fibronectin to the streptococci. The inhibitory activity was adsorbed on a column of fibronectin-Sepharose but not on a column of unsubstituted Sepharose 4B or egg albumin Sepharose. The receptor appeared to be a protein nature since the inhibitory activity of the trypsinate was destroyed by papain and was not absorbed on a column containing monoclonal antibodies directed against lipoteichoic acid bound to protein A-Sepharose. Binding sites in fibronectin for streptococci and staphylococci, respectively, were localized by analyzing the ability of isolated fragments to inhibit [125I]fibronectin binding to bacteria and by adsorbing 125I-labeled tryptic fragments with staphylococcal and streptococcal cells. Both species of bacteria appeared to preferentially bind a fragment (Mr = approximately 25,000) originating from the N-terminal region of the protein. In addition, streptococci also bound a slightly smaller fragment (Mr = approximately 23,000). Fibronectin receptors solubilized from either streptococci or staphylococci inhibited the binding of fibronectin to both species of bacteria.     

On the use of antibiotics to reduce rhizoplane microbial populations in root physiology and ecology investigations

No straightforward method exists for separating the proportion of ion exchange and respiration due to rhizoplane microbial organisms from that of root ion exchange and respiration. We examined several antibiotics that might be used for the temporary elimination of rhizoplane bacteria from hydroponically grown wheat roots ( Triticum aestivum cv. Veery 10). Each antibiotic was tested for herbicidal activity and plate counts were used to enumerate bacteria and evaluate antibiotic kinetics. Only -lactam antibiotics (penicillins and cephalosporins) did not reduce wheat growth rates. Aminoglycosides, the pyrimidine trimethoprim, colistin and rifampicin reduced growth rates substantially. Antibiotics acted slowly, with maximum reductions in rhizoplane bacteria occurring after more that 48 h of exposure. Combinations of nonphytotoxic antibiotics reduced platable rhizoplane bacteria by as much as 98%; however, this was generally a reduction from about 10⁹ to 10⁶ colony forming units per gram of dry root mass, so that many viable bacteria remained on root surfaces. We present evidence which suggests that insufficient bacterial biomass exists on root surfaces of nonstressed plants grown under well-aerated conditions to quantitatively interfere with root nitrogen absorption measurements.     

Estimation of the growth rates of epiphytic bacteria and Lemna minor in a river

SUMMARY. Growth of Lemna minor fronds in the River Frome during summer was found to be logarithmic with time and the growth rate (log₁₀) was 0.066 day⁻¹. This is equivalent to a doubling time of 4.5 days. The life expectancy of the fronds was 34 days.
The net change in the density of bacteria epiphytic on the lower surface of Lemna fronds in the R. Frome was monitored using a direct microscopic technique. The observed increase in bacterial numbers has been partitioned into the components of attachment and growth, assuming that attachment occurred at a constant rate and that the bacterial population grew logarithmically. The line which fitted the data best gave an attachment rate of 5.7 × 10⁵ bacteria cm⁻² day⁻¹ and a growth rate (log₁₀) for the bacteria of 0.044 day⁻¹ which is equivalent to a doubling time of 164 h.
Estimates of the rate of detachment of bacteria from Lemna plants were obtained from a laboratory experiment which assumed negligible growth of bacteria in 1 h. The number of bacteria which detached per hour and the sizes of the bacterial populations on the plants before and after detachment were estimated using a plating technique. Different detachment rates were monitored. The detachment rate (analogous to growth rate) which is judged to be most similar to an in situ value was 0.0031 h⁻¹ (0.074 day⁻¹). This rate added to the specific growth rate given above resulted in a corrected growth rate of 0.118 day⁻¹ equivalent to a doubling time of 61 h.     

Chitinolytic bacteria and chitin mineralization in the marine waters and sediments along the Antartic Peninsula

Abstract Chitinolytic bacteria were enumerated and isolated from marine waters and sediments along the highly productive Antarctic Peninsula. Chitinolytic bacteria were found in low concentrations (approximately 1 cell per ml) in the water column and at much higher levels in marine surface sediments (10⁴–10⁵ per g). The predominant chitinolytic bacteria isolated from the water column were identified as psychrophilic Vibrio spp. Rates of chitin mineralization were measured by collection of ¹⁴CO₂ respired from ¹⁴C-labeled chitin synthesized from chitosan and [1-¹⁴C]acetic anhydride. Chitin mineralization rates were extremely low in the marine waters analyzed (0.00085–0.0019% of the added label respired in 48 h) and appreciably higher in the marine sediments (0.0039–0.01% per 48 h), suggesting that the sediments are much more important in chitin degradation. Such low mineralization rates suggest that chitin may be accumulating in Antarctic marine sediments, though animals may also play an important role in chitin degradation.     

The Yersinia pseudotuberculosis invasin protein and human fibronectin bind to mutually exclusive sites on the alpha 5 beta 1 integrin receptor.

The Yersinia pseudotuberculosis invasin protein promotes bacterial penetration into mammalian cells by binding to several beta 1 chain integrins. We show here that proteins containing the cell-binding domain of invasin bind to the fibronectin receptor alpha 5 beta 1 isolated from human placenta and immobilized on a filter membrane. Two forms of the receptor, each having a molecular weight of about 290,000, were immunodepleted by monoclonal antibodies specific for the beta 1 subunit or the alpha 5 beta 1 heterodimer. The binding of invasin to the receptor immobolized on the filter, or to whole JAR cells, reaches saturation after 90 min and has an apparent dissociation constant (Kd) of 5.0 x 10(-9) M. Invasin binding to alpha 5 beta 1 is inhibited by the 120-kDa chymotryptic fragment of fibronectin in a competitive manner with an inhibition constant (Ki) of 7.5 x 10(-7) M. Furthermore, invasin-receptor binding is also inhibited by the hexapeptide GRGDSP, and monoclonal antibodies that block cell attachment to invasin-coated surfaces also block cell attachment to fibronectin-coated surfaces. These results indicate that invasin and fibronectin bind to the same, or closely located sites on alpha 5 beta 1, although invasin binds with a much higher affinity than does fibronectin.     

Specific monitoring by PCR amplification and bioluminescence of firefly luciferase gene-tagged bacteria added to environmental samples

Abstract The firefly luciferase gene, luc , was demonstrated to hold promise as a specific marker for monitoring of genetically modified bacteria in the environment. PCR amplification and bioluminescence procedures were modified and compared for environmental monitoring of luc -tagged bacteria, using Escherichia coli as a model. The methods were used to track luc -tagged bacterial cells added to intact sediment core microcosms. Detection limits for the luc -tagged cells were the following, expressed as cells per 0.5 g of sediment: 10², by PCR amplification; 10³, by whole cell luminescence; and 10³−10⁴, by measurement of luminescence in cell extracts.     

Antigenic heterogeneity of strains of Saccharomyces cerevisiae and Candida albicans recognised by serum antibodies from patients with Crohn''s disease

Abstract Vitronectin, a serum and extracellular matrix protein involved in immunological reactions, interacts with Helicobacter pylori strains. Of the 20 H. pylori strains tested three strains bound more than 50% of the vitronectin added, five strains bound 25–40%, nine strains bound 10–20% and three strains bound 5–8% vitronectin. Two strains, one with high- and one with low-binding properties, were selected for further characterization of ¹²⁵I-vitronectin binding. Binding to the urea-activated ¹²⁵I-labelled vitronectin was fast, saturable and reversible when an excess of unlabelled vitronectin was added to the bacteria with bound ¹²⁵I-vitronectin. The binding was heat- and protease-sensitive, suggesting that the binding was mediated by bacterial cell-surface proteins. Since components such as fetuin and orosomucoid but not asialofetuin inhibited the binding, sialic-acid specific proteins, related to H. pylori sialic-acid specific haemagglutinins, were probably involved.