Paleocene-Pleistocene benthic foraminiferal evidence of major paleoceanographic events in the eastern South Atlantic (DSDP Site 525, Walvis Ridge)

Benthic foraminifers in the size-fraction greater than 0.073 mm were studied in 88 Paleocene to Pleistocene samples from Deep Sea Drilling Project Site 525 (Hole 525A, Walvis Ridge, eastern south Atlantic). Clustering of the samples on the basis of the 86 most abundant foraminifers (in total, 331 taxa were identified) allowed separating two major assemblage zones: the Paleocene to Eocene interval, and the Oligocene to Pleistocene interval. Each of these, in turn, were subdivided into three minor subzones as follows: lower upper Paleocene (approx. 62.4 to 57.8 Ma); upper upper Paleocene (56.6 to 56.2 Ma); lower and middle Eocene (55.3 to 46.8 Ma); upper Oligocene to middle Miocene (25.3 to 16 Ma); middle Miocene to Pliocene (15.7 to 4.2 Ma); and lower Pleistocene (0.4 to 0.02 Ma), with only minor differences with the previous zone. Some very abundant taxa span most of the column studies (Bolivina huneri, Cassidulina subglobosa, Eponides bradyi, E. weddellensis, Gavelinella micra, Oridorsalis umbonatus, etc.). Several of the faunal breaks recorded coincide with conspicuous minima in the specific diversity curve, thus suggesting that the corresponding turnovers signal the final stages of periods of faunal impoverishment. At least one major bottom-water temperature drop (as derived from δ¹⁸O data) is synchronous with a decrease in the foraminiferal specific diversity. On the other hand, a specific diversity maximum in the middle Miocene might be associated with a δ¹³C increase at approx. 16 to 12 Ma. Highest foraminiferal abundances (up to 600–800 individuals per gram of dry sediment) occurred in the late Paleocene and in the early Pleistocene, in coincidence with the lowest diversity figures calculated. The magnitude of the most important faunal turnover recorded, between the middle Eocene and the late Oligocene, is magnified in our data set by the large hiatus which separates the middle Eocene from the upper Oligocene sediments. Considerably smaller overturns occurred within the late Paleocene (in coincidence with changes in the specific diversity, absolute abundance of foraminiferal tests, and δ¹³C), and in the middle Miocene (in coincidence with a specific diversity maximum and a δ¹³C excursion). New information on the morphology and the stratigraphic ranges of several species is furnished. For all the taxa recorded the number of occurrences, total number of individuals identified and first and last appearances are listed.     

Variation in the composition of fatty acids of zeaxanthin and astaxanthin monoesters in the ovary and hepatopancreas of Penaeus schmitti during ovogenesis

The carotenoid esters of the shrimp, Penaeus schmitti, were investigated by thin layer chromatography and absorption spectrophotometry. Astaxanthin monoester and zeaxanthin monoester were identified in hepatopancreas and ovaries during the sexual development. The nature of fatty acids derived from these natural esters has been determined quantitatively by gas chromatography of their methyl esters. The variations of linkage between fatty acids and carotenoids during ovogenesis are measured. The role of zeaxanthin monoester in carotenoids transfer from hepatopancreas to ovaries during this sexual development, and relations between lipid and carotenoid metabolism are discussed.     

Characteristics of galactose transport in Saccharomyces cerevisiae cells and reconstituted lipid vesicles.

Growth on galactose induces two transport processes, a high-affinity and a low-affinity process. The most important results of a comparison of the two processes were that (i) both depended on GAL2 expression, (ii) only the high-affinity process required galactokinase, (iii) both were down-regulated by catabolite inactivation, (iv) neither was significantly inhibited by carbonyl cyanide-p-trifluoromethoxy-phenyl-hydrazone, (v) neither was differentially inhibited by silver nitrate or mercuric chloride, and (vi) transport activity with a Km closer to that of the low-affinity process of whole cells was reconstituted in fused phospholipid membrane vesicles.     

Role of cyclic-AMP-dependent protein kinase in catabolite inactivation of the glucose and galactose transporters in Saccharomyces cerevisiae.

The derepressed high-affinity glucose transport system and the induced galactose transport system are catabolite inactivated when cells with these transport systems are incubated with glucose. The role of the cyclic AMP cascade in the catabolite inactivation of these transport systems was shown by using mutants affected in the activity of cyclic-AMP-dependent protein kinase (cAPK). In tpk1(w) mutants with reduced cAPK activity, the sugar transport systems were expressed but were not catabolite inactivated. In bcy1 mutants with unbridled cAPK activity resulting from a defective regulatory subunit, the transport systems were absent or present at low levels.     

Possible role of cAMP in the synthesis of β-glucanases and β-xylanases of Bacillus circulans WL-12

Abstract Bacillus circulans WL-12 secretes 1,4-β- d -xylanase and 1,3-β- d - and 1,6-β- d -glucanase activities. All of them are catabolites regulated by glucose and, while xylanase needs xylan as the inducer, the two latter enzyme activities are formed once glucose is depleted. Cyclic nucleotides such as adenosine 3',5'-monophosphate (cAMP) and guanosine 3',5' monophosphate (cGMP) exhibit a negative effect on enzyme synthesis if added to the culture media. Based on the fact that only cAMP is found in cells growing in glucose-rich media we propose a model for B. circulans WL-12 in which cAMP acts as a negative effector for regulating the synthesis of these enzymes. The model is not, however, extrapolated to other Bacillus species and all B. circulans strains.     

Genomic sequencing of two isolates of Ralstonia solanacearum causing Sergipe facies and comparative analysis with Bugtok disease isolates

Ralstonia solanacearum is the causal agent of Moko disease in bananas, which in the state of Sergipe in northeastern Brazil causes “Sergipe facies”. This disease induces atypical symptoms similar to those of Bugtok disease in the Philippines. This study was conducted to sequence, assemble, and annotate the genomes of the Sergipe facies-causing isolates SFC and IBSBF2570 (sequevar IIA-53) and compare their genomes with two representative isolates causing Bugtok disease. The genomes were sequenced and assembled, resulting in lengths of 5.58 Mb (SFC) and 5.46 Mb (IBSBF2570) in 185 and 174 contigs, respectively. The isolates of Sergipe facies and Bugtok disease showed similarities in their gene contents. We identified 5,668 information clusters, 3,752 of which were shared by all genomes (core genes). Moreover, 3,585 single-copy genes were identified. Isolates causing Bugtok disease exclusively shared 266 more information clusters than the isolates causing Sergipe facies. These results suggest that Sergipe facies and Bugtok disease isolates show high genomic similarity. However, the similarity is even greater between the Bugtok disease isolates. This may be because of their longer period of interaction compared to Sergipe facies isolates.