Enclosure experiment on the control mechanism of planktonic bacterial standing stock

In order to understand the control mechanisms of a large, stable bacterial standing stock, enclosure experiments were conducted in a eutrophic lake, where both bacterial productivity and grazing pressure were very high. Total bacterial number in the different enclosures ranged from 1.2 to 2.7×10⁷ cells mL⁻¹ throughout the experiment. The average bacterial cell production rate estimated from a grazer eliminating experiment was 6.3×10⁵ cells mL⁻¹ h⁻¹. Difference in the bacterial cell production rate between shaded and unshaded enclosures was not apparent. Bacteria showed a reduction in standing stock of only about 25–30% even after the supply of light was cut to 1%. Bacteria in the shaded enclosures then recovered their production rate in the first 12 days of perturbation. Grazing pressure in the shaded enclosures was not less than that for the control. Thus, it was considered a control mechanism of bacterial stable standing stock that the bacteria shifted their organic substrate from extracellular dissolved organic carbon freshly released from phytoplankton to that already stocked in the water column, though it is not known whether the dominant bacteria were the same.     

Mutations in a Saccharomyces cerevisme host showing increased holding stability of the heterologous plasmid pSRI

Summary We have isolated Saccharomyces cerevisiae mutants, smp, showing stable maintenance of plasmid pSRI, a Zygosaccharomyces rouxii plasmid. The smp mutants were recessive and were classified into at least three different complementation groups. The three mutants also showed increased stability of YRp plasmids and the mutations are additive for plasmid stability. One mutation, smp1, confers a respiration-deficient (rho ⁰) phenotype and several Rho^– mutants independently isolated by ethidium bromide treatment of the same yeast strain also showed increased stabilities of pSR1 and YRp plasmids. The wild-type S. cerevisiae cells showed a strongly biased distribution of pSR1 molecules as well as YRp plasmids to the mother cells at mitosis, while the smpf mutant did not show this bias. Another mutation, smp3, at a locus linked to ade2 on chromosome XV, confers temperature-sensitive growth. The SMP3 gene encodes a 59.9 kDa hydrophobic protein and disruption of the gene is lethal.     

Branching Photocycle of Sensory Rhodopsin in Halobacterium Halobium

Temperature effect of the photocyle of sensory rhodopsin (sR) was studied by nanosecond spectroscopy. Though the formation yield of sR_M (sR₃₇₀) was sharply decreased with temperature, those of sR_K (sR₆₈₀) and sR_L were insensitive to temperature changes. These results show the existence of the branching process back to sR from sR_L. The absorption maxima for sR_K and sR_L were 595 ± 5 and 555 ± 15 nm, respectively.     

Changes in Lipoxygenase Components of Rice Seedlings during Germination

Changes in lipoxygenase (LOX) activity were followed duringthe germination of rice seeds. The enzyme activity of 3-day-oldseedlings was 20 times higher than that of ungerminated seeds.Sixty per cent of the increased activity was found in shoots.The increase in LOX activity was mainly due to an increase inlipoxygenase-2 (LOX-2), a minor component in ungerminated seeds;this increase was inhibited by cycloheximide. LOX-2 was isolatedfrom the 3-day-old seedlings and compared for its enzymologicalproperties with rice lipoxygenase-3 (LOX-3), a major componentin ungerminated seeds. Both LOX-2 and LOX-3 were stable at pH5 to 8, but LOX-2 was more heatstable than LOX-3. Apparent K_mvalues of LOX-2 and LOX-3 for linoleic acid were 170 and 59µM, and those for linolenic acid were 5,300 and 88 µM,respectively. Both LOXs were inhibited by some metal ions andantioxidants. (Received February 5, 1986; Accepted May 9, 1986)     

Daphnia curvirostris Eylmann in Japanese high mountain waters (Cladocera: Daphniidae)

A species of Daphnia, Daphnia curvirostris Eylmann, found in high mountain lakes and ponds in central Japan is described. Although there were some differences in the shape of the male rostrum and the chromosome number between European populations as described by Johnson (1952) and Trentini (1980), and Japanese ones collected from high mountain waters, Japanese specimens had many characteristics similar to the taxon D. curvirostris of Europe.     

Mouse lymphoma L1210 cells acquire a new cystine transport activity upon adaptation in vitro

Summary Mouse lymphoma L1210 cells maintained in vitro at a high cell density for a certain time period adapted themselves to the in vitro environment and were able to grow indefinitely. From these adapted cells, more than 30 clones were isolated. They all had much higher activity to take up cystine than the original L1210 cells, supporting a previous view that the deficiency of the cystine uptake limits the survival and growth of L1210 cells in vitro. The cystine uptake of one cloned cell line was characterized. The enhanced uptake of cystine in these cells was mainly mediated by a Na⁺-independent, saturable system and was potently inhibited by glutamate and some other anionic amino acids, but less by aspartate. Such activity of cystine uptake was not observed in the original L1210 cells. The results suggest that, upon adaptation in vitro, L1210 cells acquire a new cystine transport activity necessary for survival and growth in vitro.     

Embryonic development,larvae and juvenile of elkhorn sculpin,Alcichthys alcicornis

The eggs ofAlcichthys alcicornis were spawned in tank at the laboratory and reared for the studies of embryonic, larval and juvenile development. This species takes place entosomatic fertilization, and females spawn fertilized eggs after copulation. The eggs are demersal and adhesive, released as a clump forming a thin layer on the bottom of tank. There was no significant difference in embryonic development between this species and other oviparous teleostean species. Hatching occurred between 17 and 18 days after spawning at a mean water temperature of 8.5?C. The newly hatched larvae averaged 4.44 mm in body length (BL). The larvae attained to post-larval stage at 5.80 mm BL, and juvenile stage at 10.2 mm BL. A specific feature of the post-larvae was the appearance of three lines of the melanophores on the caudal part of fin fold. Carotenoid first appeared on the nape at 8.70 mm BL, heavily emerged beyond 12.9 mm BL, and turned up on the back also beyond 15.2 mm BL. Scales on the lateral line were completed by 18.5 mm BL. Three pairs of flaps were observed on the dorsal surface of the head at 37.0 mm BL. External features of adult specimens are almost completed by 52.0 mm BL, yet the tip of the first preopercular was not branched but remained simple.     

Triterpenes from Periandra dulcis roots

Three oleanane triterpenes were isolated from the roots of Periandra dulcis,and identified as 3β-hydroxy-25-al-olean-18-en-30-oic acid (periandric acid I), 3β-hydroxy-25-al-olean-12-en-30-oic acid (periandric acid II) and 3-oxo-25-hydroxy-olean-12-en-30-oic acid. The former two compounds (periandric acids I and II) were identical with the aglycones obtained by hydrolysis of periandrin I and II, respectively and the latter one was a new triterpene.     

Agromonas oligotrophica gen. nov., sp. nov., a nitrogen-fixing oligotrophic bacterium

Phenotypic and chemotaxonomic characteristics of five isolates of acetylenereducing (nitrogen-fixing) oligotrophic bacteria from a paddy soil were investigated. They showed similar phenotypic characteristics: they were aerobic, asporogenous, gram-negative, motile by a polar flagellum, and irregular rods. On full strength nutrient broth (NB) growth was severely suppressed, but well supported on 10-to 10000-fold diluted NB. They consumed glucose but produced no acid, and also utilized phenolic acids such as ferulic acid or p-coumaric acid. The cellular fatty acid composition, quinone system and DNA base composition of the isolates were investigated. Cellular fatty acids mainly consisted of straightchain unsaturated C_{18 : 1} (62–81% of total fatty acids). Ubiquinone Q-10 and a high guanine-plus-cytosine content (65.1–66.0 mol%) were found. The taxonomic status of the isolates is discussed and a new genus, Agromonas, with a single species Agromonas oligotrophica sp. nov., is proposed for these isolates. The type strain of A. oligotrophica is JCM 1494.