Multiple Bacteriocin Production by Leuconostoc mesenteroidesTA33a and Other Leuconostoc/Weissella Strains

Leuconostoc (Lc.) mesenteroides TA33a produced three bacteriocins with different inhibitory activity spectra. Bacteriocins were purified by adsorption/desorption from producer cells and reverse phase high-performance liquid chromatography. Leucocin C-TA33a, a novel bacteriocin with a predicted molecular mass of 4598 Da, inhibited Listeria and other lactic acid bacteria (LAB). Leucocin B-TA33a has a predicted molecular mass of 3466 Da, with activity against Leuconostoc/Weissella (W.) strains, and appears similar to mesenterocin 52B and dextranicin 24, while leucocin A-TA33a, which also inhibited Listeria and other LAB strains, is identical to leucocin A-UAL 187. A survey of other known bacteriocin-producing Leuconostoc/Weissella strains for the presence of the three different bacteriocins revealed that production of leucocin A-, B- and C-type bacteriocins was widespread. Lc. carnosum LA54a, W. paramesenteroides LA7a, and Lc. gelidum UAL 187-22 produced all three bacteriocins, whereas W. paramesenteroides OX and Lc. carnosum TA11a produced only leucocin A- and B-type bacteriocins. Received: 11 April 1997 / Accepted: 10 June 1997     

Guaraná (Paullinia cupana) as a commercial crop in Brazilian Amazonia

Guaraná (Paullinia cupana) is a woody vine or sprawling shrub native to the central Amazon Basin. The seeds are commercially produced on some 6,000 ha in the state of Amazonas near Manaus. The principal article of commerce is an amber-colored, carbonated soft drink. It is also widely used as a high caffeine stimulant and in local medicines. The plant is monoecious and is damaged by a number of diseases, the most severe being anthracnose. Prospects are excellent for greatly expanded international markets.     

Impact of vaginal microbiome communities on HIV antiretroviral-based pre-exposure prophylaxis (PrEP) drug metabolism

Despite the efficacy of antiretroviral-based pre-exposure prophylactics (PrEP) in men who have sex with men, studies in women have produced widely varying outcomes. Recent evidence demonstrates that vaginal microbial communities are associated with increased HIV acquisition risk and may impact PrEP efficacy. Here, we investigate the mechanisms underlying how vaginal bacteria alter PrEP drug levels and impact HIV infection rates ex vivo. Using cervicovaginal lavages (CVLs) from women with or without bacterial vaginosis (BV), we identified microbial metabolism of PrEP drugs in BV samples through LC-MS/MS analysis of soluble drug levels and metabolite formation in dual T-cell cultures. CVL samples were assessed for microbiome analysis using sequencing of bacterial 16S rRNA genes. We also observed non-Lactobacillus bacteria that are associated with BV may potentially impact PrEP efficacy through increased HIV infection rates in co-cultures containing Lactobacillus or BV bacteria, PrEP drugs, CEM-GFP cells, and HIV-1_LAI virus. Finally, we used these data to develop a novel predictive mathematical simulation modeling system to predict these drug interactions for future trials. These studies demonstrate how dysbiotic vaginal microbiota may impact PrEP drugs and provides evidence linking vaginal bacteria to PrEP efficacy in women.     

Suppression of the rotifer Polyarthra remata by the omnivorous copepod Tropocyclops extensus: predation or competition

Indirect evidence from observations in the field suggested thata common and often abundant cyclopoid copepod, Tropocyclopsextensus, despite its small size (0.5 mm) and largely algaldiet, is an important predator of the rotifer Polyarthra remata.Laboratory experiments showed that copepodids and adults, butnot nauplii, markedly suppressed the population growth of thisrotifer. The suppression could be attributed entirely to predation,rather than to exploitative competition for shared food resourcesor to interference. Mortality rates predicted from a separatefeeding-rate experiment weresufficient to account for the declinein population size observed in the Tropocyclops treatment ofculture experiments. Also, monitoring the availability of cryptomonadfood in treatments with and without Tropocyclops throughoutthese experiments showed that cryptomonad densities always remainedhigh and were just as high or significantly higher in the copepodtreatments. Furthermore, direct videographic observations ofP. remata from cultures with and without Tropocyclops demonstratedno significant differences in swimming velocity, tendency todeviate from a straight-line path, or frequency and length ofspontaneous escape responses. Per capita ingestion rates ofT. extensus on P. remata varied from 2 to 8 day^-1, were significantlyhigher for adult females than adult males or copepodids V, andincreased significantly with rotifer density. A tendency ofcopepods to have higher ingestion rates on young than adultrotifers was not significant. Copepods cultured since birthwith cryptomonads and P. remata ate significantly fewer rotifersthan those cultured only with cryptomonads; this may be explainedby a more sated condition of the former and provided no evidencefor the idea that previous experience with this rotifer mightincrease predation efficiency. The results show that T. extensusin natural communities has the potential to deplete naturalpopulations of susceptible rotifer prey. Accordingly, it mayshift the species structure of rotifer assemblages in favourof resistant species, and provide selection pressure for avoidanceresponses.     

CORRESPONDENCE BETWEEN PHYLOGENY AND MORPHOLOGY OF SNOWELLA SPP. AND WORONICHINIA NAEGELIANA,CYANOBACTERIA COMMONLY OCCURRING IN LAKES1

In this study, the first reported isolates of the genera Snowella and Woronichinia were characterized by 16S rRNA gene sequencing and morphological analysis. Phylogenetic studies and sequences for these genera were not available previously. By botanical criteria, the five isolated strains were identified as Snowella litoralis (Häyrén) Komárek et Hindák Snowella rosea (Snow) Elenkin and Woronichinia naegeliana (Unger) Elenkin. This study underlines the identification of freshly isolated cultures, since the Snowella strains lost the colony structure and were not identifiable after extended laboratory cultivation. In the 16S rRNA gene analysis, the Snowella strains formed a monophyletic cluster, which was most closely related to the Woronichinia strain. Thus, our results show that the morphology of the genera Snowella and Woronichinia was in congruence with their phylogeny, and their phylogeny seems to support the traditional botanical classification of these genera. Furthermore, the genera Snowella and Woronichinia occurred commonly and might occasionally be the most abundant cyanobacterial taxa in mainly oligotrophic and mesotrophic Finnish lakes. Woronichinia occurred frequently and also formed blooms in eutrophic Czech reservoirs.     

The presence of chlorophyll b and the estimation of phaeopigments in marine phytoplankton

A reverse-phase h.p.l.c. technique was used to estimate theconcentration of chlorophyll b in phytoplankton cultures, fecalpellets of Calanus pacificus, and suspended paniculate matterfrom the Central North Pacific, Oregon coastal waters, and DabobBay (a temperate fjord in Puget Sound, WA, USA). The purposewas to assess the distribution of this pigment in the euphoticzone and its effect on the fluorometnc estimation of phaeopigments.Analyses of natural waters confirm high chlorophyll b concentrations(median mass ratio of b:a > 0.3) at the depth of the chlorophylla maximum in tropical waters while values for temperate planktonare relatively low (median mass ratio of chl b:a = 0.05) andpatchy. Zooplankton fecal pellets showed a significant enrichmentin chlorophyll b, suggesting grazing as a mechanism to explainhigh concentrations of this pigment at the bottom of the euphoticzone. It is estimated that the presence of chlorophyll b couldcause an average overestimation of phaeopigment concentrationby the fluorometnc technique of 38% between 0 and 200 m in theCentral North Pacific. This effect is more pronounced at thelayer of chlorophyll b maximum (120–140 m). ¹Present address: Marine Biology Research Division, A-002, ScrippsInstitution of Oceanography, La Jolla, CA 92093, USA     

Micropropagation of Calluna vulgaris cv. ‘H.E. Beale’

Axillary shoot producing cultures were obtained from microcuttings and shoot tips of Calluna vulgaris cv. H.E. Beale. For cultures derived from microcuttings the highest multiplication rate of 38 shoots (5 mm or longer) was obtained on a reduced salt medium with the addition of 0.5 mgl^-1 2-isopentenyladenine (2iP) during an 8 week subculture. For shoot tip derived cultures 0.2 mgl^-1 6-benzyladenine (BA) was the best cytokinin and led to a multiplication rate of 26 for a 6 week subculture. The addition of 1 g/l casein hydrolysate to a multiplication medium enhanced shoot proliferation in presence of 0.5 mgl^-1 BA.Despite various auxin treatments shoots formed no roots in vitro but rooted readily if transferred to a peat substrate ex vitro. A high rooting percentage (80%) was also obtained with shoots taken from the end of a multiplication phase and rooted directly. An additional subculture on low auxin containing media before transfer to peat substrate is recommended because the shoot condition can be improved in this way. A high number of rooted plantlets was produced, so the methods described will allow mass propagation.     

Characterization of a light-dependent glutamate synthase activity in Chlamydomonas reinhardtii

Photosynthetically active vesicles prepared from Chlamydomonas reinhardtii retained a light-dependent glutamate synthase activity which was highly specific for 2-oxoglutarate (K_m=2.1 mM) and L-glutamine (K_m=0.9 mM) as amido group acceptor and donor respectively. This activity was inhibited by azaserine, p-hydroxymercuribenzoate and 3-(p-chlorophenyl)-1,1-dimethyl urea.Light-dependent synthesis of glutamate was also obtained by coupling Chlamydomonas photosynthetic particles to purified ferredoxin-glutamate synthase, using ascorbate and 2,6-dichlorophenol-indophenol as electron donor. This system was also specific for 2-oxoglutarate (K_m=1 mM) and L-glutamine (K_m=0.8 mM) as substrates, and was stimulated by dithioerythritol. Azaserine and p-hydroxymercuribenzoate, but not 3-(p-chlorophenyl)-1,1-dimethyl urea, inhibited the reconstituted activity; high concentrations of 2-oxoglutarate were inhibitory.Abbreviations A Absorbance - CCP p-Trichlorometoxi-carbonylcyanide-phenylhydrazone - Chl Chlorophyll - CMU 3-(p-Chlorophenyl)-1,1-dimethyl urea - DPIP 2,6-Dichlorophenol-indophenol - DTE Dithioerythritol - MSX L-Methionine, D-L, sulfoximine - MV Methyl viologen     

Mutants of the Rous sarcoma virus envelope glycoprotein that lack the transmembrane anchor and cytoplasmic domains: analysis of intracellular transport and assembly into virions.

The envelope glycoprotein complex of Rous sarcoma virus consists of a knoblike, receptor-binding gp85 polypeptide that is linked through disulfide bonds to a membrane-spanning gp37 spike. We used oligonucleotide-directed mutagenesis to assess the role of the hydrophobic transmembrane region and hydrophilic cytoplasmic domain of gp37 in intracellular transport and assembly into virions. Early termination codons were introduced on either side of the hydrophobic transmembrane region, and the mutated env genes were expressed from the late promoter of simian virus 40. This resulted in the synthesis of glycoprotein complexes composed of a normal gp85 and a truncated gp37 molecule that lacked the cytoplasmic domain alone or both the cytoplasmic and transmembrane domains. The biosynthesis and intracellular transport of the truncated proteins were not significantly different from those of the wild-type glycoproteins, suggesting that any protein signals for biosynthesis and intracellular transport of this viral glycoprotein complex must reside in its extracellular domain. The glycoprotein complex lacking the cytoplasmic domain of gp37 is stably expressed on the cell surface in a manner similar to that of the wild type. In contrast, the complex lacking both the transmembrane and cytoplasmic domains is secreted as a soluble molecule into the media. It can be concluded, therefore, that the transmembrane domain alone is essential for anchoring the RSV env complex in the cell membrane and that the cytoplasmic domain is not required for anchor function. Insertion of the mutated genes into an infectious proviral genome allowed us to assess the ability of the truncated gene products to be assembled into virions and to determine whether such virions were infectious. Viral genomes encoding the secreted glycoprotein were noninfectious, whereas those encoding a glycoprotein complex lacking only the cytoplasmic domain of gp37 were infectious. Virions produced from these mutant-infected cells contained normal levels of glycoprotein. The cytoplasmic tail of gp37 is thus not required for the assembly of envelope glycoproteins into virions. It is unlikely, therefore, that this region of gp37 interacts with viral core proteins during the selective incorporation of viral glycoproteins into the viral envelope.