Temporal dynamics of estuarine phytoplankton: A case study of San Francisco Bay

Detailed surveys throughout San Francisco Bay over an annual cycle (1980) show that seasonal variations of phytoplankton biomass, community composition, and productivity can differ markedly among estuarine habitat types. For example, in the river-dominated northern reach (Suisun Bay) phytoplankton seasonality is characterized by a prolonged summer bloom of netplanktonic diatoms that results from the accumulation of suspended particulates at the convergence of nontidal currents (i.e. where residence time is long). Here turbidity is persistently high such that phytoplankton growth and productivity are severely limited by light availability, the phytoplankton population turns over slowly, and biological processes appear to be less important mechanisms of temporal change than physical processes associated with freshwater inflow and turbulent mixing. The South Bay, in contrast, is a lagoon-type estuary less directly coupled to the influence of river discharge. Residence time is long (months) in this estuary, turbidity is lower and estimated rates of population growth are high (up to 1–2 doublings d^–1), but the rapid production of phytoplankton biomass is presumably balanced by grazing losses to benthic herbivores. Exceptions occur for brief intervals (days to weeks) during spring when the water column stratifies so that algae retained in the surface layer are uncoupled from benthic grazing, and phytoplankton blooms develop. The degree of stratification varies over the neap-spring tidal cycle, so the South Bay represents an estuary where (1) biological processes (growth, grazing) and a physical process (vertical mixing) interact to cause temporal variability of phytoplankton biomass, and (2) temporal variability is highly dynamic because of the short-term variability of tides. Other mechanisms of temporal variability in estuarine phytoplankton include: zooplankton grazing, exchanges of microalgae between the sediment and water column, and horizontal dispersion which transports phytoplankton from regions of high productivity (shallows) to regions of low productivity (deep channels).Multi-year records of phytoplankton biomass show that large deviations from the typical annual cycles observed in 1980 can occur, and that interannual variability is driven by variability of annual precipitation and river discharge. Here, too, the nature of this variability differs among estuary types. Blooms occur only in the northern reach when river discharge falls within a narrow range, and the summer biomass increase was absent during years of extreme drought (1977) or years of exceptionally high discharge (1982). In South Bay, however, there is a direct relationship between phytoplankton biomass and river discharge. As discharge increases so does the buoyancy input required for density stratification, and wet years are characterized by persistent and intense spring blooms.     

Analysis of Dysgenesis-Induced Lethal Mutations on the X Chromosome of a Q Strain of DROSOPHILA MELANOGASTER

The Q strain known as v6 was tested for its ability to induce X-linked lethal mutations in male and female hybrids from crosses with M strains in the P-M system of hybrid dysgenesis. All measurements of the mutation rate were made on the X chromosome derived from the v6 strain. The lethal rate for young hybrid males from the cross M female X v6 male was 1.11% per chromosome. For older males, it was only 0.44%, suggesting that there is less mutational or more repair activity in the germ cells of the older males or that mutant cells are selectively eliminated as the hybrid males age. The lethal rate for hybrid females from comparable crosses was approximately the same for both ages that were tested. However, it was substantially less than the rate for the hybrid males--only 0.26% per chromosome. Genetically identical hybrid females from reciprocal crosses also showed a low mutation rate, 0.13% per chromosome. Again, there was no difference between young and old flies. Mapping experiments established that most of the lethal mutations that were recovered from the male and female hybrids were located in two regions on the X chromosome, one between bands 14B13 and 15A9 , the other between bands 19A1 and 20A , which encompasses the maroonlike locus. More refined mapping of the lethals in the maroonlike region demonstrated that the vast majority of these affected a single gene located in band 19C4 . Cytological analysis of the lethal chromosomes revealed that several carried rearrangements, including inversions, duplications and deficiencies. Chromosome breakage occurred primarily in bands 14D1 -3 and 18F- 20A , and most of the breaks in the latter segment were located in 19C . However, rearrangements involving 19C and mutations of the gene in 19C4 were mutually exclusive events. In situ hybridization of a P element probe to the chromosomes of v6 demonstrated that P elements reside at a minimum of five sites on the X chromosome. These P element sites correspond to the mutational and breakage hot spots on that chromosome. The combined genetic and cytological data imply that most of the X-linked lethal mutations that occur in M X v6 hybrids are due to local P element action. Consideration of these and other data suggest that v6 is a weak P strain in the P-M system of hybrid dysgenesis and that other Q strains might also be regarded in this way.     

Iron transport in Streptomyces pilosus mediated by ferrichrome siderophores, rhodotorulic acid, and enantio-rhodotorulic acid

Streptomyces pilosus is one of several microbes which produce ferrioxamine siderophores. In the accompanying paper (G. Müller and K. Raymond, J. Bacteriol. 160:304-312), the mechanism of iron uptake mediated by the endogenous ferrioxamines B, D1, D2, and E was examined. Here we report iron transport behavior in S. pilosus as mediated by the exogenous siderophores ferrichrome, ferrichrysin, rhodotorulic acid (RA), and synthetic enantio-RA. In each case iron acquisition depended on metabolic energy and had uptake rates comparable to that of [55Fe]ferrioxamine B. However, the synthetic ferric enantio-RA (which has the same preferred chirality at the metal center as ferrichrome) was twice as effective in supplying iron as was the natural ferric RA complex, suggesting that stereospecific recognition at the metal center is involved in the transport process. Iron uptake mediated by ferrichrome and ferric enantio-RA was strongly inhibited by kinetically inert chromic complexes of desferrioxamine B. These inhibition experiments indicate that iron from these exogenous siderophores is transported by the same uptake system as ferrioxamine B. Since the ligands have no structural similarity to ferrioxamine B except for the presence of three hydoxamate groups, we conclude that only the hydroxamate iron center and its direct surroundings are important for recognition and uptake. This hypothesis is supported by the fact that ferrichrome A and ferrirubin, which are both substituted at the hydroxamate carbonyl groups, were not (or were poorly) effective in supplying iron to S. pilosus.     

Changes with time in the distribution of virus and PR protein around single local lesions of TMV infected tobacco

Summary ELISA was used to determine PR la protein and TMV accumulation in local necrotic lesions produced on salicylic acid and water sprayed Nicotiana tabacum cv Xanthi-nc leaves. The amount of PR la protein produced is the result of an interaction between the salicylic acid treatment and lesion growth. The implication of these observations for experiments investigating the relationship between PR proteins and resistance are discussed.The distribution of TMV and PR la protein in and around single local necrotic lesions up to 14 days after inoculation was measured by ELISA. The highest concentration of TMV was in the centre of the lesion and decreased rapidly with distance from the centre. In contrast there was very little PR la protein in the centre of the lesion, the largest amounts were just outside the centre, and the concentration then decreased with distance from the centre. This is the distribution that might be expected for a substance closely associated with the restriction of virus spread.     

Nomograms for Calculation of Heat Loss

Two nomograms are presented. The first enables the mean surface and body temperatures and the body heat content of a patient of given weight to be determined from measurements of skin temperature at three sites and of the core (rectal) temperature. The second enables the change in heat content of such a patient to be determined from the change in mean body temperature.     

Karyological and biochemical evidence for chromosomal dedifferentiation in neoplasia

Summary Quantitative analysis of the X-linked enzyme, glucose 6-phosphate dehydrogenase (G-6-PD), was performed on tumor cells lines from two human females. Both tumor cells were hyperdiploid, having complete or redundant C+X groups. One, no. 930, lacked the X chromatin body and exhibited twice the level of G-6-PD as in the X chromatin-positive tumor cells, ME-180. Hence, in the no. 930 cell, reversal of X chromosomal condensation was associated with loss of the X chromatin body and doubling of genetic activity. Cells of no. 930 were subsequently placed in culture where after three passages they developed an X chromatin body (or bodies). G-6-PD determinations made at that time showed enzyme levels comparable to the X chromatin-positive tumor cells (ME-180). This research was supported by United States Public Health Service Grant CA 08791-03.     

Biological Ion Exchanger Resins: II. QUERP Water and Ion Exchange Selectivity

Biological selectivity is shown to vary with medium osmotic strength and temperature. Selectivity reversals occur at 4°C and at an external osmolality of 0.800 indicating that intracellular hydration and endosolvent (intracellular water) structure are important determinants in selectivity. Magnetic resonance measurements of line width by steady-state nuclear magnetic resonance (NMR) indicate a difference in the intracellular water signal of 16 Hz between the K form and Na form of Escherichia coli, providing additional evidence that changes in the ionic composition of cells are accompanied by changes in endosolvent structure. The changes were found to be consistent with the thermodynamic and magnetic resonance properties of aqueous electrolyte solutions. Calculation of the dependence of ion-pairing forces on medium dielectric reinforces the role of endosolvent structure in determining ion exchange selectivity.     

Anisotropic Absorption of Linearly Polarized Light by Cylindrical Molecules

A general theory relating the orientation of the transition moment in a chromophore to incident light, linearly polarized at an arbitrary angle, is discussed for cylindrical molecules. Experimental verification of this theory is presented for molecules of tobacco mosaic virus (TMV), T₂ DNA, and polyadenylic acid (poly-A).