Effect of Planting Unit Size and Sediment Stabilization on Seagrass Transplants in Western Australia

Abstract The effect of increasing planting unit size and stabilizing sediment was examined for two seagrass planting methods at Carnac Island, Western Australia in 1993. The staple method (sprigs) was used to transplant Amphibolis griffithii (J. M. Black) den Hartog and the plug method was used to transplant A. griffithii and Posidonia sinuosa Cambridge and Kuo. Transplant size was varied by increasing the number of rhizomes incorporated into a staple and increasing the diameter of plugs. Planting units were transplanted into bare sand, back into the original donor seagrass bed, or into a meadow of Heterozostera tasmanica, which is an important colonizing species. Sprigs of A. griffithii were extracted from a monospecific meadow; tied into bundles of 1, 2, 5, and 10 rhizomes; and planted into unvegetated areas. Half the units were surrounded by plastic mesh and the remainder were unmeshed. All treatments were lost within 99 days after transplanting, and although larger bundles survived better than smaller ones, no significant differences could be attributed to the effects of mesh or sprig size. Plugs of P. sinuosa and A. griffithii were extracted from monospecific meadows using polyvinyl chloride pipe of three diameters, 5, 10, and 15 cm, and planted into unvegetated areas nearby. Half the units were surrounded by plastic mesh and the remainder were unmeshed. Posidonia sinuosa plugs were also placed within a meadow of H. tasmanica (Martens ex Aschers.) den Hartog. Only 60% of A. griffithii plug sizes survived 350 days after transplanting back into the donor bed; however, survival of transplants at unvegetated areas varied considerably, and analysis of variance indicated a significant two‐way interaction between treatment and plug size. Transplants survived better when meshed (90% survived) and survival improved with increasing plug size. Posidonia sinuosa transplants survived poorly (no plugs survived beyond 220 days in bare or meshed treatments) regardless of size. Survival of 10‐ and 15‐cm plugs was markedly better than the 5‐cm plugs in vegetated areas, including the H. tasmanica meadow. The use of large seagrass plugs may be appropriate for transplantation in high‐energy wave environments.     

Contribution of pilA to Competitive Colonization of the Squid Euprymna scolopes by Vibrio fischeri

Vibrio fischeri colonizes the squid Euprymna scolopes in a mutualistic symbiosis. Hatchling squid lack these bacterial symbionts, and V. fischeri strains must compete to occupy this privileged niche. We cloned a V. fischeri gene, designated pilA, that contributes to colonization competitiveness and encodes a protein similar to type IV-A pilins. Unlike its closest known relatives, Vibrio cholerae mshA and vcfA, pilA is monocistronic and not clustered with genes associated with pilin export or assembly. Using wild-type strain ES114 as the parent, we generated an in-frame pilA deletion mutant, as well as pilA mutants marked with a kanamycin resistance gene. In mixed inocula, marked mutants were repeatedly outcompeted by ES114 (P < 0.05) but not by an unmarked pilA mutant, for squid colonization. In contrast, the ratio of mutant to ES114 CFUs did not change during 70 generations of coculturing. The competitive defect of pilA mutants ranged from 1.7- to 10-fold and was more pronounced when inocula were within the range estimated for V. fischeri populations in Hawaiian seawater (200 to 2,000 cells/ml) than when higher densities were used. ES114 also outcompeted a pilA mutant by an average of twofold at lower inoculum densities, when only a fraction of the squid became infected, most by only one strain. V. fischeri strain ET101, which was isolated from Euprymna tasmanica and is outcompeted by ES114, lacks pilA; however, 11 other diverse V. fischeri isolates apparently possess pilA. The competitive defect of pilA mutants suggests that cell surface molecules may play important roles in the initiation of beneficial symbioses in which animals must acquire symbionts from a mixed community of environmental bacteria.     

Production of superoxide dismutases from Proteus mirabilis and Proteus vulgaris

Proteus mirabilis and Proteus vulgaris expressed a combination of superoxide dismutase (Sod) activities, which was assigned to FeSod1, FeSod2 and MnSod for P. mirabilis, and FeSod, MnSod and CuZnSod for P. vulgaris. Production of the Sod proteins was dependent on the availability of iron, whether cells were grown under anaerobiosis or aerobiosis and growth phase. Nalidixic acid and chloramphenicol inhibited cell growth and the iron- and dioxygen-dependent production of Sod. These results support the involvement of metal ions and redox status in the production of Proteus Sods.     

Induction of haemolytic activity in Escherichia coli by the slyA gene product

The Salmonella typhimurium protein SlyA_ST, originally described as a cytolysin, shows sequence similarities to several known bacterial regulatory proteins. A homologue to the slyA_St gene has been localised to min 37 of the Eschericia coli K-12 chromosome and has been designated slyA_EC When introduced in trans on a plasmid, the slyA_EC gene conferred a haemolytic phenotype on wild-type but not clyA-knockout strains of E. coli K-12. The clyA gene encodes a novel haemolysin that is not expressed by wild-type E. coli under tested laboratory conditions. Western and Northern blot analyses, and DNA-band-shift assays support a model whereby the SlyA_EC protein activates clyA expression by binding to the clyA promoter region, thereby supporting the sequence similarity data in suggesting that SlyA_ST is a haemolysin activator rather than being a haemolysin per se.     

GENETIC TRANSFORMATION OF THE DIATOMS CYCLOTELLA CRYPTICA AND NAVICULA SAPROPHILA

Two species of diatoms were genetically transformed by introducing plasmid vectors containing the Escherichia coli neomycin phosphotransferase II (npt II ) gene. Expression of the bacterial npt II gene in the diatoms was achieved using the putative promoter and terminator sequences from the acetyl-CoA carboxylase gene from the centric diatom Cyclotella cryptica T13L Reimann, Lewin, and Guillard. The vectors were introduced into C. cryptica and the pennate diatom Navicula saprophila NAVIC1 Lange-Bertalot and Bonik by microprojectile bombardment. Putative transformants were selected based on their ability to grow in the presence of the antibiotic G418, and production of the neomycin phosphotransferase protein by the transformed cells was confirmed by western blotting. The foreign DNA integrated into one or more random sites within the genome of the transformed algal cells, often in the form of tandem repeats. This is the first report of reproducible, stable genetic transformation of a chlorophyll c -containing alga .     

Gene rearrangements in Chlamydomonas chloroplast DNAs are accounted for by inversions and by the expansion/contraction of the inverted repeat

To gain insight into the mutational events responsible for the extensive variation of chloroplast DNA (cpDNA) within the green algal genus Chlamydomonas, we have investigated the chloroplast gene organization of Chlamydomonas pitschmannii, a close relative of the interfertile species C. eugametos and C. moewusii whose cpDNAs have been well characterized. At 187 kb, the circular cpDNA of C. pitschmannii is the smallest Chlamydomonas cpDNA yet reported; it is 56 and 105 kb smaller than those of its C. eugametos and C. moewusii counterparts, respectively. Despite this substantial size difference, the arrangement of 77 genes on the C. pitschmannii cpDNA displays only three noticeable differences from the organization of the corresponding genes on the collinear C. eugametos and C. moewusii cpDNAs. These changes in gene order are accounted for by the expansion/contraction of the inverted repeat and one or two inversions in a single-copy region. In land plant cpDNAs, these kinds of events are also responsible for gene rearrangements. The large size difference between the C. pitschmannii and C. eugametos/C. moewusii cpDNAs is mainly attributed to multiple events of deletions/additions as opposed to the usually observed expansion/contraction of the inverted repeat in land plant cpDNAs. We also found that the mitochondrial genome of C. pitschmannii is a circular DNA molecule of 16.5 kb which is 5.5 and 7.5 kb smaller than its C. moewusii and C. eugametos counterparts, respectively.     

A note on dimensionless life histories for birds versus mammals

Summary Offspring production over the adult lifespan (b/M whereb is the yearly fledgling or offspring production and 1/M is the mean adult lifespan) is an approximate invariant within both birds and mammals. The two taxa differ, however, in that mammals have bothM and b as invariants (b/M = b/M) while birds do not ( is the age at first breeding). Birds have a surprising cancellation in that bothM andb are ^–0.25.     

Specific Activity of Brain Palmitoyl-CoA Pool Provides Rates of Incorporation of Palmitate in Brain Phospholipids in Awake Rats

Abstract: In vivo rates of palmitate incorporation into brain phospholipids were measured in awake rats following programmed intravenous infusion of unesterified [9,10-³H]palmitate to maintain constant plasma specific activity. Animals were killed after 2–10 min of infusion by microwave irradiation and analyzed for tracer distribution in brain phospholipid and phospholipid precursor, i.e., brain unesterified palmitate and palmitoyl-CoA, pools. [9,10-³H]Palmitate incorporation into brain phospholipids was linear with time and rapid, with >50% of brain tracer in choline-containing glycerophospholipids at 2 min of infusion. However, tracer specific activity in brain phospholipid precursor pools was low and averaged only 1.6–1.8% of plasma unesterified palmitate specific activity. Correction for brain palmitoyl-CoA specific activity increased the calculated rate of palmitate incorporation into brain phospholipids (0.52 nmol/s/g) by ∼60-fold. The results suggest that palmitate incorporation and turnover in brain phospholipids are far more rapid than generally assumed and that this rapid turnover dilutes tracer specific activity in brain palmitoyl-CoA pool owing to release and recycling of unlabeled fatty acid from phospholipid breakdown.     

Phalaenopsis bellina (Rchb.f.) Christenson,a segregate from P. violacea Witte (Orchidaceae: Aeridinae)

A reevaluation of floral and vegetative morphology together with data from analysis of floral fragrance and flavonoid co-pigment chemistry suggest that specific status is warranted for the two kinds ofPhalaenopsis violacea Witte known informally as the “Bornean type” and the “Malayan type.”Phalaenopsis violacea var.bellina Rchb.f. is elevated to specific rank, providing a name for the “Bornean type” plants.     

The effects of weed strips on aphids and aphidophagous predators in an apple orchard

Selected weeds were used to attract antagonists of apple aphids in an apple orchard near Berne, Switzerland. In the year before the experiment, in 1991, the apple aphidsDysaphis plantaginea (Pass.) andAphis pomi (DeGeer) and aphidophagous predators were homogenously distributed in the orchard. In April 1992, weed strips were sown between tree rows and along the border parallel to the first and the last row of trees in one part (the other part served as control). In both parts of the orchard, randomly chosen tress were controlled visually in weekly intervals in 1992 and 1993. During flowering of weeds more aphidophagous predators were observed on the apple trees within the strip-sown area than in the control area. The most abundant and permanent aphidophagous predators were spiders, predaceous Heteroptera, Coccinellidae, and Chrysopidae. Both species of aphids were significantly less abundant in the area with weed strips than in the control area during the vegetation period. The effects of the weed strips on aphidophagous predators, and those of predators on aphids, are discussed.