Adenylyl cyclase and G-proteins in Phytomonas

Phytomonas sp. membranes have an adenylyl cyclase activity which is greater in the presence of Mn2+ than with Mg2+. The Mg2+ and Mn2+ activity ratio varies from one membrane preparation to another, suggesting that the adenylyl cyclase has a variable activation state. A[35S]GTP-gamma-S-binding activity with a Kd of 171 nM was detected in Phytomonas membranes. Incubation of these membranes with activated cholera or pertussis toxin and [adenylate 23P]NAD+ led to incorporation of radioactivity into bands of about 40-44 kDa. Crude membranes were electrophoresed on SDS-polyacrylamide gels and analyzed, by Western blotting, with the 9188 anti-alpha[s] antibody and the AS/7 antibody (anti-alpha[i], anti-alpha[i1], and anti-alpha[i2]. These procedures resulted in the identification of polypeptides of approximately 40-44 kDa. Phytomonas adenylyl cyclase could be activated by treatment of membrane preparations with cholera toxin, in the presence of NAD+, while similar treatment with pertussis toxin did not affect this enzyme activity. These studies indicate that in Phytomonas, adenylyl cyclase activity is coupled to an unknown receptor entity through G alpha[s] proteins.     

An Immunological Assay for Detection and Enumeration of Thermophilic Biomining Microorganisms

A specific, fast, and sensitive nonradioactive immunobinding assay for the detection and enumeration of the moderate thermophile Thiobacillus caldus and the thermophilic archaeon Sulfolobus acidocaldarius was developed. It employs enhanced chemiluminescence or peroxidase-conjugated immunoglobulins in a dot or slot blotting system and is very convenient for monitoring thermophilic bioleaching microorganisms in effluents from industrial bioleaching processes.     

Modeling approach to control of carbohydrate metabolism during citric acid accumulation by Aspergillus niger: II. Sensitivity analysis

Steady state sensitivity analysis of a model of carbohydrate metabolism and anaplerotic synthesis of oxalacetate were, in Aspergillus niger under conditions of citric acid accumulation, carried out. The flux and metabolite concentration control structure of the system obtained shows that the hexokinase/substrate transport step is the main controlling step of the pathway. The quantitative contribution of the other enzyme catalyzed or transport steps are also discussed. These results allow the design of a proper strategy of biotechnological manipulation aimed at improvement of the process. (c) 1994 John Wiley & Sons, Inc.     

Chemical composition of antarctic zooplankton during austral fall and winter

Water level, ash content, proximate (protein, lipid, carbohydrate and chitin) and elemental (carbon and nitrogen) composition were analyzed in twentythree species of Antarctic Zooplankton collected during the austral fall (1986) and winter (1988) from the Scotia/Weddell Sea region. Extremes in water level, ash content and organic components were typified by copepods and gelatinous forms. Ostracods and polychaetes were generally similar in composition to copepods, being only slightly higher in water level and ash content. Chaetognaths exhibited a composition intermediate in character with some components similar in value to that shown by crustaceans (i.e. protein) while other components were more in the range of values seen in gelatinous forms (i.e. water level and ash content). Protein was the major proximate component and measured values (as % Afdw) were fairly uniform among non-gelatinous species (x=33.9±6.9). Lipid levels were variable, with high values (>30% AFDW) only found for the copepods Calanoides acutus, Calanus propinquus and Euchaeta antarctica. Carbohydrate values were low in all species examined. Chitin was measured in crustacean species only. With the exception of C. acutus (x=2.5% AFDW chitin), values were similar among species with mean values being slightly higher in fall (x=11.8±2.5) than in winter (x=6.7±1.8). Among non-gelatinous species, the ratio of carbon to nitrogen was positively correlated with the lipid to protein ratio, underscoring the compositional association between elemental and proximate components in these groups. In gelatinous species, the relationship between carbon:nitrogen and lipid:protein was inconsistent and less pronounced. Caloric content was estimated from recovered organic matter for nongelatinous species. As a function of wet weight and dry weight, values reflected differences in water level and ash content among individual species. As a function of ashfree dry weight, values were similar among all species (x=3.6±0.9 kcal/g).Seasonal comparisons were possible for 12 of the 23 species. Among crustaceans, changes in water level and organic components were variable reflecting dissimilar trophic, reproductive or ecological habits among different species. Essentially no change in composition between fall and winter was observed for diapause species (e.g. Calanoides acutus and Rhincalanus gigas) as well as for omnivorous/ carnivorous species (e.g. Gaetanus tenuispinus). Conversely, large compositional changes were evident for Calanus propinquus, a small-particle grazer that relies heavily on lipid reserves. Chaetognaths and some gelatinous species exhibited a considerable decrease in ash content from fall to winter which, for most cases, was mirrored by some degree of increase in lipid level. At present, however, scant data are available to help explain the observed patterns of compositional change within non-crustacean species.     

Genetic construction and functional analysis of hybrid polyketide synthases containing heterologous acyl carrier proteins.

The gene that encodes the acyl carrier protein (ACP) of the actinorhodin polyketide synthase (PKS) of Streptomyces coelicolor A3(2) was replaced with homologs from the granaticin, oxytetracycline, tetracenomycin, and putative frenolicin polyketide synthase gene clusters. All of the replacements led to expression of functional synthases, and the recombinants synthesized aromatic polyketides similar in chromatographic properties to actinorhodin or to shunt products produced by mutants defective in the actinorhodin pathway. Some regions within the ACP were also shown to be interchangeable and allow production of a functional hybrid ACP. Structural analysis of the most abundant polyketide product of one of the recombinants by electrospray mass spectrometry suggested that it is identical to mutactin, a previously characterized shunt product of an actVII mutant (deficient in cyclase and dehydrase activities). Quantitative differences in the product profiles of strains that express the various hybrid synthases were observed. These can be explained, at least in part, by differences in ribosome-binding sites upstream of each ACP gene, implying either that the ACP concentration in some strains is rate limiting to overall PKS activity or that the level of ACP expression also influences the expression of another enzyme(s) encoded by a downstream gene(s) in the same operon as the actinorhodin ACP gene. These results reaffirm the idea that construction of hybrid polyketide synthases will be a useful approach for dissecting the molecular basis of the specificity of PKS-catalyzed reactions. However, they also point to the need for reducing the chemical complexity of the approach by minimizing the diversity of polyketide products synthesized in strains that produce recombinant polyketide synthases.     

Exploring the legacy of African and Indigenous Caribbean admixture in Puerto Rico

Objectives

From an anthropological genetic perspective, little is known about the ethnogenesis of African descendants in Puerto Rico. Furthermore, historical interactions between Indigenous Caribbean and African descendant peoples that may be reflected in the ancestry of contemporary populations are understudied. Given this dearth of genetic research and the precedence for Afro-Indigenous interactions documented by historical, archeological, and other lines of evidence, we sought to assess the biogeographic origins of African descendant Puerto Ricans and to query the potential for Indigenous ancestry within this community.

Materials and Methods

Saliva samples were collected from 58 self-identified African descendant Puerto Ricans residing in Puerto Rico. We sequenced whole mitochondrial genomes and genotyped Y chromosome haplogroups for each male individual (n = 25). Summary statistics, comparative analyses, and network analysis were used to assess diversity and variation in haplogroup distribution between the sample and comparative populations.

Results

As indicated by mitochondrial haplogroups, 66% had African, 5% had European, and 29% had Indigenous American matrilines. Along the Y chromosome, 52% had African, 28% had Western European, 16% had Eurasian, and, notably, 4% had Indigenous American patrilines. Both mitochondrial and Y chromosome haplogroup frequencies were significantly different from several comparative populations.

Discussion

Biogeographic origins are consistent with historical accounts of African, Indigenous American, and European ancestry. However, this first report of Indigenous American paternal ancestry in Puerto Rico suggests distinctive features within African descendant communities on the island. Future studies expanding sampling and incorporating higher resolution genetic markers are necessary to more fully understand African descendant history in Puerto Rico.     

Trophic structure in open waters of the marginal ice zone in the Scotia-Weddell confluence region during spring (1983)

The structure of the food web was investigated in open waters adjacent to the marginal ice zone in the southern Scotia Sea in spring 1983. Diets were defined for dominant zooplankton, micronekton, and flying seabird species and then aggregated by cluster analysis into feeding groups. Most zooplankton were omnivorous, feeding on phytoplankton, protozoans, and in some cases, small metazoans (copepods). Only two species were found to be exclusively herbivorous:Calanoides acutus andRhincalanus gigas. Micronekton were carnivores with copepods being the dominant prey in all their diets. The midwater fishElectrona antarctica was the dominant food item in seven of the nine seabird species examined. Cephalopods, midwater decapod shrimps and carrion were also important in the diets of a few seabird species. Comparison (cluster analysis) of diets in spring with other seasons (winter, fall) indicated that over half the species examined (18 of 31) had similar diets in all seasons tested. The significant intraspecific shifts in diet that did occur were attributable to regional, seasonal, and interannual effects. A scheme is presented that describes the major energetic pathways through the open water ecosystem from phytoplankton to apex predators. At the base are phytoplankton and protozoans which are the principal food resource for the biomass copepods and krill. Krill and the biomass copepods are the principal forage of the midwater fishElectrona antarctica which, in turn, is the central diet component of flying seabirds as well as important food for the Antarctic fur seal and cephalopods. Krill are a major diet element for the fur seal and cephalopods, and the principal food of the minke whale.