Cleavage of lambda repressor and synthesis of RecA protein induced by transferred UV-damaged F sex factor

Summary Transfer of a UV-damaged F sex factor to a recipient lysogen induces prophage development. Under these conditions RecA protein synthesis was induced and repressor cleaved, as observed upon direct induction, that is, when the recipient lysogen was directly exposed to UV-light. The efficiency of induction of RecA protein synthesis in recipient bacteria which had received an irradiated F-lac factor was about 80% of that measured upon direct induction. We observed the simultaneous disappearance of repressor and a slight production of cleavage fragments; quantitation by densitometric scanning of the autoradiogram after correction for the efficiency of transfer indicated that 55% of repressor was cleaved. Transfer of UV-damaged Hfr DNA failed to induce RecA protein synthesis. A phage vector carrying oriF, the cloned origin of F plasmid replication, after exposure to UV-light and infection of a recipient lysogen, induced RecA protein synthesis and a moderate but significant cleavage of repressor. Indirect induction by UV-damaged F sex factor or phage oriF resulted in biochemical cellular reactions similar to those observed upon direct induction. LexA repressor that negatively controls RecA protein synthesis appeared more susceptible to cleavage than did repressor.     

Carotenoids from plankton and photosynthetic bacteria in sediments as indicators of trophic changes in Lake Lobsigen during the last 14000 years

Previous examination of drilling cores showed that the majority of the carotenes and carotenoids originally present in the various planktonic organisms and phototrophic bacteria are preserved in sediments. The indicator pigments for algae phyla are: Lutein for Chlorophyta, Myxoxanthophylls and their derivatives for Cyanophyta, Fucoxanthin for Chrysophyta, and Alloxanthin for Cryptophyta.The pigments in the deepest sediment sample (late glacial time, clay, 12.83 m) consists primarily of Alloxanthin, secondly of Lutein and -carotene and thirdly of traces of Okenone, Speroidenone and other such bacterial carotenoids. The first plankton organisms were thus Cryptophyta and some Chlorophyta. The presence of the phototrophic bacteria pigments indicates that at the time of sediment formation, anaerobic conditions prevailed at the lake bottom.The Holocene era commences at a depth of 8.55 m and is characterized by the first occurrence of Myxoxanthophyll and Echinenone from Cyanophyta, as well as by a rapid increase of -carotene, Lutein and Alloxanthin. The pronounced occurrence of Oscillatoria rubescens (blood of the Burgundies), characterized by Oscillaxanthin at 8.21 m must be considered for Swiss lakes as a very surprising discovery.The intensive plankton production again lead to stringent anaerobic conditions. Predominant among phototrophic bacteria pigments were Okenone, Spheroidene and Rhodopin.     

Dispersion patterns of phytoplankton in lakes

The spatial distribution of phytoplankton is considered in relation to factors which may cause deviations from a random distribution. Such deviations may arise over a wide range of scales and attention is focused on small-scale contagion and its possible significance. Evidence is presented that contagion may occur at scales smaller than have previously been considered. Samples covering a range of volumes from 0.1 ml to 10 ml were taken from a small lake and total numbers of several phytoplankton species were counted in each sample to avoid problems arising from sub-sampling. The counts were used to calculate different indices of dispersion. All indices indicated contagion to occur at the scale being considered. Within the range examined the patch size appeared variable between species. The possible derivation and relevance of such micro-patchiness is discussed.     

CYP175A1 from<Emphasis Type="Italic"> Thermus thermophilus</Emphasis> HB27, the first β-carotene hydroxylase of the P450 superfamily

The biological function of thermostable P450 monooxygenase CYP175A1 from Thermus thermophilus HB27 was studied by functional complementation in Escherichia coli. The gene product of CYP175A1 added hydroxyl groups to both rings of -carotene to form zeaxanthin (,-carotene-3,3-diol) in E. coli, which produces -carotene due to the Erwinia uredovora carotenoid biosynthesis genes. In addition, spectroscopic methods revealed that E. coli carrying CYP175A1 and the cDNA of the Haematococcus pluvialis carotene ketolase was able to synthesise hydroxyechinenone. The predicted amino acid sequence of the enzyme from T. thermophilus does not show substantial similarity with other known -carotene hydroxylases, but 41% with the cytochrome P450 monooxygenase from Bacillus megaterium (CYP102A1, P450 BM3). It is concluded that CYP175 A1 represents a new type of -carotene hydroxylase of the P450 superfamily.     

Seasonal succession of phytoplankton in a lake of the Paraná river floodplain,Argentina

Phytoplankton biomass, morphological and taxonomic composition, species diversity and productivity were analyzed in a shallow lake of the Middle Paraná River floodplain (El Tigre, 31 ° 41 S and 60° 42 W), between November 1986 and July 1988. Lake inundation (filling and through-flow phases) constituted an intense long-term perturbation in the physical and chemical environment. As the lake filled with river water, K-selected species (netplanktonic filamentous bluegreens, > 37 µm, with low surface area/volume (SA/V) ratios) that had existed prior to filling (late spring 1986) were replaced in summer-fall by r-selected species (nannoplanktonic chlorophytes and cryptophytes, < 37 µm, mainly stout forms with high SA/V ratios). During the through-flow phase, lentic phytoplankton was replaced by lotic flagellate populations due to the direct flushing by river water. During the period of falling water (drainage and isolation phases), nanoplanktonic algae with similar characteristics to those of the filling phase dominated in late winter-spring. Later in the isolation phase, these were succeeded by K-selected species (netplanktonic algae, mainly motile spherical dinoflagellates and filamentous bluegreens with low SA/V ratios). Simultaneously, primary production per unit biomass decreased and total biomass and specific diversity increased. Seasonal changes of phytoplankton in floodplain lakes can be interpreted as the interaction between true successional development (as observed in the drainage and isolation phases) and intermediate disturbance. Using Reynolds' terminology, short-term disturbance (slight inflow of nutrient-rich river water) caused reversion to an earlier stage in the former succession, and long-term disturbance (lake inundation) truncated the successional progression and a new (or shifted) succession was initiated.     

Amylolytic enzymes produced by a color variant strain ofAureobasidium pullulans

A color variant strain ofAureobasidium pullulans (NRRL Y-12974) produced amylase and -glucosidase activities when grown at 28°C for 4 days in liquid culture on a wide variety of carbon sources such as starch, pullulan, glucose, maltose, cyclodextrins, sucrose, xylose, and xylan. An -glucosidase was separated by Q-Sepharose adsorption from the cell-free culture broth and partially purified by hydroxylapatite and octyl-Sepharose chromatography. After ammonium sulfate treatment of the culture supernatant (obtained after Q-Sepharose adsorption), the amylase fraction was separated into three active fractions by hydroxylapatite column chromatography, which were identified as -amylase, glucoamylase A, and glucoamylase B. The glucoamylase A was further purified by octyl-Sepharose column chromatography. The pH optima for the action of -amylase, glucoamylase A, glucoamylase B, and -glucosidase were 5.0, 4.5, 4.0–4.5, and 4.5, respectively. The -amylase and glucoamylase B were fully stable at pH 3.0–6.0, glucoamylase A at pH 4.5–5.5, and -glucosidase at pH 3.5–7.0 for 1 h at 50°C. The optimum temperatures for the action of these enzymes were 55°, 50°–60°, 65°, and 65°C, respectively. The -amylase, glucoamylase A, and glucoamylase B were adsorbed onto raw corn starch and degraded it. Glucoamylase B readily cleaved pullulan. The -glucosidase was not adsorbed onto raw starch and did not degrade it at all. It hydrolyzed both -1,4 and -1,6 linkages in oligosaccharides. All four enzymes did not require any metal ion for activity and were inhibited by cyclodextrins (-and -, 10mm).     

A quantitative study of the effects of different grades of polyvinyl alcohol on the activities of certain enzymes in unfixed tissue sections

Synopsis Different grades of the colloid stabilizer, polyvinyl alcohol, used for protecting unfixed cryostat sections during cytochemical reactions, may have different effects on enzymatic activity. The influence of three grades of polyvinyl alcohol on the activities of soluble, membrane-bound and membrane-enclosed enzymes has been investigated in unfixed sections; the activities were measured microdensitometrically.The largest molecular weight polyvinyl alcohol (G18/140, mol. wt. about 90 000) did not retain glucose-6-phosphate dehydrogenase activity in sections of rat liver even when used at the maximum convenient concentration (12%); G04/140 and M05/140 (molecular weights of 15 000 and 25 000 respectively) retained this soluble enzyme if used at concentrations of 30 and 20% respectively.At these concentrations, lactate dehydrogenase activity was apparently decreased when G04/140 and M05/140 were used; this diminished activity has been shown to be due to the need to establish optimal concentrations of reactants for each grade of polyvinyl alcohol and for each reaction. When optimal concentrations of reactants were used, the activities of this enzyme in the presence of each grade of polyvinyl alcohol were identical.The presence of any type of polyvinyl alcohol did not influence the activities of mitochondrial succinate dehydrogenase or of the smooth endoplasmic reticulum enzyme, 5,3-hydroxysteroid dehydrogenase. However, the presence of polyvinyl alcohol improved the state of the section.     

A single plant technique for field studies of distribution of32P-labelled phosphate between plant and soil pools

Summary ³²P-labelled monocalcium phosphate solution was supplied to the root system of individual wheat plants within a field crop two weeks after emergence. Three levels of carrier P, equivalent to 2.5, 5, and 10 kgP ha^–1 were used. The distribution of³²P between shoots and the soil inorganic and organic P fractions was measured after a further six weeks growth.There was no evidence for the incorporation of³²P-orthophosphate into soil organic P fractions in the wheat rhizosphere in the period between germination and mid-tillering.The suitability of the single plant technique to measure plant available P in field soils was assessed by calculating A values from plants grown in soil witth different fertilizer P histories. There was a significant linear relationship between A values and the amount of soil P extractable with 0.5M NaHCO₃ from the different fertilizer treatments. Although the technique is unlikely to given an absolute value for plant available nutrient, it can provide quantitative data for comparative trials with different forms of fertilizer, methods of fertilizer application or amounts of available soil water. The values obtained should be termed comparative A values or A^c values.     

Stability of fumarase activity of Brevibacterium flavum immobilized with ϰ-carrageenan and Chinese gallotannin

Summary In order to improve L-malic acid productivity by Brevibacterium flavum immobilized with -carrageenan, addition of Chinese gallotannin to the immobilization medium was investigated. As the results show, the optimal concentration of Chinese gallotannin was 0.1% (w/v). Fumarase activity and the stability of this improved preparation were higher than in one with only -carrageenan. Addition of Chinese gallotannin was more advantageous to stability towards ethanol than addition of polyethyleneimine. The L-malic acid productivity of the immobilized cells at 37°C was 42.2 kg/h per 1,000 l column, and increased threefold compared with that of B. flavum immobilized with only -carrageenan, and was 25 times that of B. ammoniagenes immobilized with polyacrylamide. Persimmon tannin also increased the stability of fumarase.     

Relationship between cyclic AMP level and accumulation of carotenoid pigments in Neurospora crassa

Dark grown mycelial cells of Neurospora crassa bearing mutant genes crisp-I or frost and having a decreased level of cyclic adenosine 3,5-monophosphate contained more carotenoid pigments than the cells with wild alleles of these genes. A transient decrease of the cyclic AMP occurred following photoinduction of carotenoid synthesis during its lag-period. Its intensity correlated with the increase of carotenoid pigment level due to photoinduction. No correlation in the content of cyclic guanosine 5-phosphate with both constitutive level of carotenoids and its photoinduced increase was observed.     

Carotenoid pigments in a red strain of Rhizobium from Lotononis bainesii Baker

The carotenoid pigments of a Rhizobium strain isolated from Lotononis bainesii were found to be diglucosyl-4,4-diapocarotene-4,4-dioate and glucosyl-4,4-diapocarotene-4-oate-4-oic acid.5th publication in the series Carotenoids of Rhizobia [4th publication: Helv. chim. Acta 62: 2551–2557 (1979)]     

Visual and lenticular pigments in the eyes of demersal deep-sea fishes

We report on the lens pigmentation and visual pigments of 52 species of demersal deep-sea fishes caught at depths ranging from 480 m to 4110 m in the Porcupine Seabight and Goban Spur area of the North-eastern Atlantic. Only one species, caught between 480 and 840 m, had a lens with large amounts of pigment, consistent with the hypothesis that heavily pigmented lenses in deep-sea fish serve to enhance the contrast of bioluminescent signals by removing much of the background radiance, which is only visible to fish living shallower than 1000 m. Low concentrations of lens pigmentation were also observed in a further two species (Rouleina attrita and Micromesisteus poutassou). The retinae of all species except five, contained only a single visual pigment, as determined by microspectrophotometry of individual rods, and/or spectrophotometry of retinal wholemounts and retinal extracts. Those fishes caught between 500 m and 1100 m had wavelengths of peak sensitivity (_max) ranging from 476 nm to 494 nm, while most fish living below 1100 m tended to be more conservative with (_max) values ranging from 475 nm to 485 nm. The only exceptions to this were three deep-living species caught between 1600 m and 2000 m whose retinae contain abnormally short-wave sensitive visual pigments (Cataetyx laticeps — _max 468 nm; Alepocephalus bairdii — _max 467 nm; Narcetes stomias _max 472 nm), suggesting adaptation for the detection of short-wave bioluminescence.     

Phycobiliproteins — a family of valuable,widely used fluorophores

Phycobiliproteins are brilliantly colored, highly fluorescent components of the photosynthetic light-harvesting antenna complexes of cyanobacteria (blue-green algae), red algae and cryptomonads. These proteins carry covalently attached linear tetrapyrrole pigments related structurally to biliverdin. Phycobiliproteins, purified from certain organisms, are isolated as either trimers, ()₃, of approximatelyM _r 110–120×10³ (e.g., allophycocyanins), or hexamers, ()₆, of aboutM _r 250×10³ (certain phycoerythrins). Three phycobiliproteins R-phycoerythrin, B-phycoerythrin, and allophycocyanin serve as valuable fluorescent tags with numerous applications in flow cytometry, fluorescence activated cell sorting, histochemistry and, to a limited degree, in immunoassay and detection of reactive oxygen species. These applications exploit the unique physical and spectroscopic properties of phycobiliproteins.     

Prochlorococcus marinus nov. gen. nov. sp.: an oxyphototrophic marine prokaryote containing divinyl chlorophyll a and b

Several years ago, prochlorophyte picoplankton were discovered in the N. Atlantic. They have since been found to be abundant within the euphotic zone of the world's tropical and temperate oceans. The cells are extremely small, lack phycobiliproteins, and contain divinyl chlorophyll a and b as their primary photosynthetic pigments. Phylogenies constructed from DNA sequence data indicate that these cells are more closely related to a cluster of marine cyanobacteria than to their prochlorophyte relatives Prochlorothrix and Prochloron. Several strains of this organism have recently been brought into culture, and herewith are given the name Prochlorococcus marinus.     

Colonization of artificial substrates by benthos in a second-order high altitude river in Kenya

An investigation on the colonization of artificial substrate baskets by benthos was carried out in the Naro Moru River, a second-order high altitude river in Kenya, from November, 1986 to October, 1987. Simuliidae dominated the colonizing benthos. The mean (±95% CL) maximum colonization time was achieved after 9.63±1.57 days. The highest mean diversity (H) occurred after 6 days of exposure whilst the highest mean H_maximum, evenness (J) and species richness (s) were achieved after 10, 8 and 10 days respectively.The benthos arrival rate (AR) declined exponentially with time. The changes in benthos departure rate (DR) with time was insignificant. Equilibrial state (AR:DR=1.0) was not achieved in the present study.     

Distribution and breeding biology of offshore cichlids in Lake Malawi/ Niassa

Synopsis Lake Malawi/Niassa is the second largest rift valley lake in Africa, with an area of 28 800 km², and an average and maximum depth of 292 m and>700 m, respectively. The lake is well known for the great diversity of fish occurring in the inshore zone. However, the offshore fish community is poorly documented. To rectify this, regular sampling was undertaken over two years, using trawl and gillnets at six offshore locations. This paper reports on the species composition, spatial distribution and breeding biology of the dominant cichlids species from the offshore pelagic zone. Cichlids formed approximately 88% of the offshore fish biomass. Most abundant were two species of zooplanktivores in the genus Diplotaxodon that made up 71% of the offshore fish biomass. An undescribed species, given the cheironym D. bigeye, was mainly found at a depth of 220 m during the day, but moved into near surface waters at night when the moon was full. This species was absent from the shallow regions of the lake. The most abundant offshore species was D. limnothrissa, which was distributed evenly throughout the lake to depths of 220 m. A less common offshore zooplanktivore was Copadichromis quadrimaculatus that formed 5% of the biomass and was confined to the upper 100 m of the water column. The main piscivores were in the genus Rhamphochromis and formed approximately 10% of the offshore fish biomass. The two dominant taxa were R. longiceps and the large Rhamphochromis group, and both were more common in the southern half of the lake. The former occurred mainly in the upper 100 m of the water column and the latter mainly at depths of 100–150 m. The length at maturity and fecundity for the dominant offshore species were estimated and seasonal breeding cycles determined from gonad activity and gonado-somatic indices.     

A new isolate of the rhodospirillum fulvum group and its photosynthetic pigments

Summary The present paper reports the isolation of an obligate phototrophic bacterium which belongs to the Rhodospirillum fulvum-group on the basis of its colour, morphology, nutritional requirements and strictly anaerobic nature. p-Aminobenzoic acid was shown to be the only growth factor required. Rhsp. fulvum synthesizes bacteriochlorophyll a as its only chlorophyllous pigments. The carotenoid composition comprises lycopene (I) and rhodopin (II) as the major components; traces of 1,2,1,2-tetrahydro-1,1-dihydroxy-lycopene (III) were also present.

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Zusammenfassung Es wird die Isolierung eines obligat phototrophen Bakteriums beschrieben, welches auf Grund seiner Farbe, Morphologie, Nährstoff-Bedürfnisse und streng anaeroben Lebensweise in die Rhodospirillum fulvum-Gruppe eingeordnet wird. Als einzigen Wachstumsfaktor benötigt der Stamm p-Aminobenzoesäure. Rhsp. fulvum bildet Bacteriochlorophyll a als einzigen chlorophyllartigen Farbstoff. Die Hauptmenge der Carotinoide besteht aus Lycopin (I) und Rhodopin (II); es sind außerdem Spuren von 1,2,12-Tetrahydro-1,1-dihydroxy-Lycopin (III) nachgewiesen.

     

The influence of prey hardness on Daphnia's selectivity for large prey

Two comparable methods were used to study the feeding of four species of Daphnia on large spherical particles which differed in size and hardness. The first method used gut analysis to estimate the selectivities of daphnids feeding in a broad size range of a single particle type, including polystyrene beads (4–60 µm diameter) in the laboratory and Eudorina colonies (10–90 µm) in the field. In the second method, Daphnia of different sizes fed in a mixture of 6.5 µm Chlamydomonas and one of eight test particles. Smaller daphnids were less effective in feeding on large test particles. Nonlinear regression was therefore used to estimate the Daphnia body size at which the clearance rate on a test particle was reduced to 50% of that for Chlamydomonas. The results of both methods show that prey size and hardness are both very important in determining daphnid feeding selectivity. For a given particle size, soft algae (naked and gelatinous flagellates) are more readily ingested than hard algae (diatoms and dinoflagellates), and hard algae are more readily ingested than polystyrene beads. Daphnia can feed effectively on algae that are 2–5 times larger than the largest ingestible bead.     

Carotenoids in some ultraviolet mutants of Epicoccum nigrum link

Summary Mutants were produced by ultraviolet irradiation of the mould Epicoccum nigrum Link. The qualitative and quantitative formation of carotenoid pigments was studied. In addition to the four carotenoids present in the wild-type strain 5-I-3 several other carotenoids were isolated and identified.The presence of these pigments is discussed. The results support the proposed pathway for the biosynthesis of rhodoxanthin, 3,3-diketo-retro--carotene, from -carotene.