A total of 48 pathovars of Pseudomonas syringae and eight related species were studied by DNA-DNA hybridization (51 nuclease method) and ribotyping. The existence of nine discrete genomospecies was indicated. Genomospecies 1 corresponded to P. syringae sensu strict0 and included P. syringae pathovars syringae, aptata, lapsa, papulans, pisi, atrofaciens, aceris, panici, dysoxyli and japonica. Genomospecies 2 included P. syringae pathovars phaseolicola, ulmi, mori, lachrymans, sesami, tabaci, morsprunorum, glycinea, ciccaronei, eriobotryae, mellea, aesculi, hibisci, myricae, photiniae and dendropanacis and nome n s pec i e s Pseudomonas sa vastanoi, Pseudomonas ficuserectae, Pseudomonas meliae and Pseudomonas amygdali, which are thus synonymous. P. amygdali is the earliest valid name for this genomospecies. Genomospecies 3 included P. syringae pathovars tomato, persicae, antirrhini, maculicola, viburni, berberidis, apii, delphinii, passiflorae, p hiladelp hi, ribicola and primulae. We recommend strain CFBP 2212 of P. syringae pv. tomato to serve as the type strain. Genomospecies 4 included 'Pseudomonas coronafaciens' and P. syringae pathovars porri, garcae, striafaciens, atropurpurea, oryzae and zizaniae and corresponds to 'P. coronafaciens'. Genomospecies 5 included P. syringae pv. tremae and corresponds to Pseudomonas tremae sp. nov. Genomospecies 6 included Pseudomonas viridiflava and the presently misidentified pathotype strains of P. syringae pv. ribicola and P. syringae pv. primulae and thus corresponds to P. viridiflava. Genomospecies 7 included P. syringae pv. tagetis and P. syringae pv. helianthi. We recommend strain CFBP 1694 of P. syringae pv. tagetis to serve as a reference strain. Genomospecies 8 included P. syringae pv. theae and Pseudomonas avellanae and thus corresponds t o P. avellanae. Genomospecies 9 included P. syringae pv. cannabina and corresponds to Pseudomonas cannabina sp. nov. Ribotyping (Smal and Hincll endonucleases) could separate seven of the nine genomospecies. The unnamed genomospecies 3 and 7 will be named when phenotypic data are available for identification. Two species are described,P. tremae sp. nov. and P. cannabina sp. nov. Other species will be named when phenotypic data are available for identification. 1965 1942 1959 1968 1967 1957 1957 19681969 1957 1979 19491970 1956 1968 196119741991 1951 1935 1957 1968 1965 1923 19581974 1978 1983 196319621974 19491982 19831969 1978 19491984 1939 1967 1946 1961 1961 1966 1971 1959 1972 1976 1970 1970 1960 1972 1987 1979 1958 1983 1959 1974 1978 1977 1967 1976 1976 1976 1976 1958 1977 1974 1950 1964 1965 1965 1927 NK NK NK * Janse et al. (1996). Keywordsal., 1992). Fluorescent phytopathogenic pseudomonads cluster with species of the genus Pseudomonas sensu stricto, within rRNA-similarity group I (Palleroni, 1984), corresponding to the y branch of the Proteobacteria (Kersters et al., 1996).The taxonomy of Pseudomonas syringae and relate...

Summary Cylindrospermopsis raciborskii occupies a rapidly expanding geographical area. Its invasive success challenges eutrophication control in many lakes. To understand better the load‐dependent behaviour of this nitrogen fixing cyanobacterium under in situ conditions, we studied P‐dependent growth of a C. raciborskii strain under continuous and pulsed P supply. The Droop model reasonably described P‐dependent growth in the continuously supplied chemostats. Large P pulses, however, caused a delay in growth and cells subject to P pulses grew slower than their counterparts with the same P quota supplied continuously. The kinetics of P uptake indicated that C. raciborskii is opportunistic with respect to P. Its high excess P storage capacity after a saturating P pulse (Qex=95 µg P [mg C]‐1) and P‐specific uptake capacity (Umax = Vmax/QP=150–1200) are indicative of storage adaptation. At the same time, the affinity of the P uptake system (Umax/K = 800–4000) is also high. Rate of leakage exceeded that of the steady state net P uptake by one to two orders of magnitude. Growth affinity of C. raciborskii (µmax/Kµ≈ 20) was relatively low, presumably due to the substantial leakage. The dynamics of the particular water body determine which trait contributes most to competitive success of C. raciborskii. In deep lakes with vertical nutrient gradients, the cyanobacterium may rely primarily on its high P storage capacity, which is coupled to a lack of short‐term feedback inhibition and efficient buoyancy regulation. In lakes without such gradients, high P uptake affinity may be vitally important.

The current fossil fuel reserves are not sufficient to meet the increasing demand and very soon will become exhausted. Pollution, global warming, and inflated oil prices have led the quest for renewable energy sources. Algal biofuels represent a potential source of renewable energy. Algae, as the third generation feedstock, are suitable for biodiesel and bioethanol production due to their quick growth, excellent biomass yield, and high lipid and carbohydrate contents. With their huge potential, algae are expected to surpass the first and second generation feedstocks. Only a few thousand algal species have been investigated as possible biofuel sources, and none of them was ideal. This review summarizes the current status of algal biofuels, important steps of algal biofuel production, and the major commercial production challenges.

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1. This study introduces delayed fluorescence (DF) excitation spectroscopy as an on-line tool for in situ monitoring of the composition and biomass of various colour classes of phytoplankton when they are photosynthetically active (cyanobacteria, chlorophytes, chromophytes and cryptophytes). The DF data are validated by comparison with those from conventional methods (weekly microscopic counts and the measurement of chlorophyll concentration). 2. The composition of phytoplankton as assessed by DF agreed reasonably well with the results from microscopic counts, particularly when differences in chlorophyll-specific DF integrals of the various colour classes were taken into account. 3. Integrals of DF spectra were converted into concentration of chlorophyll a using empirical factors derived from field data. The value of the conversion factor was nearly twice as high when the relative abundance of cyanobacteria was low (<15%) than when it was high. The converted DF-chl time series agreed well with chlorophyll measurements particularly when blooms were developing. As the DF method is inherently free of the interference caused by pigment degradation products, the discrepancy between the two data sets increased during the collapse of blooms and when sediment resuspension was intense. 4. Fourier spectrum analysis of the time series of DF-chl indicated that samples must be taken, at a minimum, every 2-3 days to capture the dynamics of phytoplankton. As a consequence, the dynamics of various algal blooms, including their timing, duration and net growth rate, could be estimated with greater confidence than by using conventional methods alone. 5. On-line DF spectroscopy is an advanced technique for monitoring daily the biomass and composition of the photosynthetically active phytoplankton in aquatic environments, including turbid shallow lakes. At present, the detection limit is around 1 mg DF-chl a m )3 in terms of total biomass but confidence in estimates of phytoplankton composition declines sharply below about 5 mg chl a m )3 . 6. On-line DF spectroscopy represents a promising approach for monitoring phytoplankton. It will be useful in water management where it can act as an early-warning system of declines in water quality. In basic ecological research it can supplement

The aim of this research was to test whether NH 4 ? and NO 3 -affect the growth, P demand, cell composition and N 2 fixation of Cylindrospermopsis raciborskii under P limitation. Experiments were carried out in P-limited (200 lg l -1 PO 4 -P) chemostat cultures of C. raciborskii using an inflowing medium containing either 4,000 lg l -1 NH 4 -N, 4,000 lg l -1 NO 3 -N or no combined N. The results showed the cellular N:P and C:P ratios of C. raciborskii decreased towards the Redfield ratio with increasing dilution rate (D) due to the alleviation of P limitation. The cellular C:N and carotenoids:chlorophyll-a ratios also decreased with D, predominantly as a result of an increase in the chlorophyll-a and N content. The NH 4 ? and NO 3 -supply reduced the P maintenance cell quota of C. raciborskii. Consequently, the biomass yield of the N 2 -grown culture was significantly lower. The maximum specific growth rate of N 2 -grown culture was also the lowest observed. It is suggested that these differences in growth parameters were caused by the P and energy requirement for heterocyte formation, nitrogenase synthesis and N 2 fixation. N 2 fixation was partially inhibited by NO 3 -and completely inhibited by NH 4? . It was probably repressed through the high N content of cells at high dissolved N concentrations. These results indicate that C. raciborskii is able to grow faster and maintain a higher biomass under P limitation where a sufficient supply of NH 4 ? or NO 3 -is maintained. Information gained about the species-specific nutrient and pigment stoichiometry of C. raciborskii could help to access the degree of nutrient limitation in water bodies.

Forty bacterial strains isolated from leek blight (Allium porrum) in France and other countries were studied by conventional biochemical methods, serological reactions, numerical taxonomy, DNA-DNA hybridization, and ice nucleation activity, as well as by pathogenicity on leek and other host plants. They were compared with reference strains of Pseudomonas, mainly pathotype strains of P. syringae pathovars and strains of P. syringae pv. syringae isolated from various host plants including onions. Leek strains sorted with P. syringae species (sensu lato) by LOPAT tests (production of levan-sucrase, oxidase, pectinase, arginine dihydrolase, and hypersensitive reaction on tobacco). Leek strains were pathogenic to leek and produced symptoms identical to those observed in the field. They were the only strains in our study that could cause blight of leek. Thus, our results justify the creation of a new pathovar. Leek strains constituted a highly homogeneous DNA group and a discrete phenon by numerical taxonomy, and they belonged to O-serogroup POR. The name of P. syringae pv. porri is proposed for the bacterium causing leek blight. Criteria for routine identification are presented and taxonomic status is discussed.