The metabolic switch can be activated in a recombinant strain of <Emphasis Type="Italic">Streptomyces lividans</Emphasis> by a low oxygen transfer rate in shake flasks

Background

In Streptomyces, understanding the switch from primary to secondary metabolism is important for maximizing the production of secondary metabolites such as antibiotics, as well as for optimizing recombinant glycoprotein production. Differences in Streptomyces lividans bacterial aggregation as well as recombinant glycoprotein production and O-mannosylation have been reported due to modifications in the shake flask design. We hypothetized that such differences are related to the metabolic switch that occurs under oxygen-limiting conditions in the cultures.

Results

Shake flask design was found to affect undecylprodigiosin (RED, a marker of secondary metabolism) production; the RED yield was 12 and 385 times greater in conventional normal Erlenmeyer flasks (NF) than in baffled flasks (BF) and coiled flasks (CF), respectively. In addition, oxygen transfer rates (OTR) and carbon dioxide transfer rates were almost 15 times greater in cultures in CF and BF as compared with those in NF. Based on these data, we obtained respiration quotients (RQ) consistent with aerobic metabolism for CF and BF, but an RQ suggestive of anaerobic metabolism for NF.

Conclusion

Although the metabolic switch is usually related to limitations in phosphate and nitrogen in Streptomyces sp., our results reveal that it can also be activated by low OTR, dramatically affecting recombinant glycoprotein production and O-mannosylation and increasing RED synthesis in the process.

     

STUDIES IN PENNATE DIATOMS: VALVE MORPHOLOGIES OF LICMOPHORA AND CAMPYLOSTYLUS1

Using scanning electron and light, microscopy, several hundred specimens of Campylostylus normanianus (Grev.) Gerloff, Licmophora abbreviata Agardh, L. gracilis var. anglica (Kütz) Per. et Per., and L. flabellata (Carm.) Agardh were examined to elucidate their valve morphology. These species were found to be heterovalvar with respect to the presence of the labiate process in the basal apices of the cell, although one was always present at the head pole of each valve. This form of heterovalvar may be one basis for partitioning the large and variable family Diatomaceae. Because of the similar valve morphologies exhibited by C. normanianus and Licmophora species examined, it is recommended that Campylostylus normanianus be placed in the older genus Licmophora, as L. normaniana (Grev.) Wahrer.     

PSEUDO-NITZSCHIA SPECIES (BACILLARIOPHYCEAE) IN LOUISIANA COASTAL WATERS: MOLECULAR PROBE FIELD TRIALS, GENETIC VARIABILITY, AND DOMOIC ACID ANALYSES

An 18-month field survey of the Pseudo-nitzschia population present in Louisiana coastal waters was conducted comparing species abundance estimates by novel fluorescent molecular probes (16S large subunit rDNA oligonucleotide sequences) with traditional electron and differential-interference light microscopy. While the probe and microscopic analyses agreed on the presence or absence of four common Pseudo-nitzschia species ( P. multiseries (Hasle) Hasle, P. pseudodelicatissima (Hasle) Hasle, P. delicatissima (P.T. Cleve) Heiden, and P. pungens (Grunow) Hasle in 66% of the samples analyzed, the probes gave conflicting results with the microscopic methods in the remaining 34% of the samples. The majority of the discrepancies appear to be because of genetic variation within the Pseudo-nitzschia population, especially in P. pseudodelicatissima, indicating that the Monterey Bay Pseudo-nitzschia spp. may not be appropriate reference strains for distinguishing Louisiana Pseudo-nitzschia spp. Additionally, P. pseudodelicatissima has been associated with domoic acid (DA) activity in three field samples, at levels up to 22 times higher than the highest value given inother published reports of DA production by this species. The contemporaneous existence of multiple strains of P. pseudodelicatissima (toxic and non-toxic) presents new challenges to the study of the ecophysiology and population dynamics of this bloom-forming species.     

Phylogenetic patterns of trait and trait plasticity evolution: Insights from amphibian embryos

Environmental variation favors the evolution of phenotypic plasticity. For many species, we understand the costs and benefits of different phenotypes, but we lack a broad understanding of how plastic traits evolve across large clades. Using identical experiments conducted across North America, we examined prey responses to predator cues. We quantified five life‐history traits and the magnitude of their plasticity for 23 amphibian species/populations (spanning three families and five genera) when exposed to no cues, crushed‐egg cues, and predatory crayfish cues. Embryonic responses varied considerably among species and phylogenetic signal was common among the traits, whereas phylogenetic signal was rare for trait plasticities. Among trait‐evolution models, the Ornstein–Uhlenbeck (OU) model provided the best fit or was essentially tied with Brownian motion. Using the best fitting model, evolutionary rates for plasticities were higher than traits for three life‐history traits and lower for two. These data suggest that the evolution of life‐history traits in amphibian embryos is more constrained by a species’ position in the phylogeny than is the evolution of life history plasticities. The fact that an OU model of trait evolution was often a good fit to patterns of trait variation may indicate adaptive optima for traits and their plasticities.     

Intermediate host switches drive diversification among the largest trematode family: evidence from the Polypipapiliotrematinae n. subf. (Opecoelidae), parasites transmitted to butterflyfishes via predation of coral polyps

Podocotyloides stenometra Pritchard, 1966 (Digenea: Opecoelidae) is the only trematode known to infect anthozoan corals. It causes disease in coral polyps of the genus Porites Link (Scleractinia: Poritidae) and its life-cycle depends on ingestion of these polyps by butterflyfishes (Perciformes: Chaetodontidae). This species has been reported throughout the Indo-Pacific, from the Seychelles to the Galápagos, but no study has investigated whether multiple species are involved. Here, we recollect P. stenometra from its type-host and type-locality, in Hawaiian waters, and describe four new species from examination of 768 butterflyfishes from French Polynesia. On the basis of morphology, phylogeny and life-history, we propose Polypipapiliotrema Martin, Cutmore & Cribb n. gen. and the Polypipapiliotrematinae Martin, Cutmore & Cribb n. subf., for P. stenometra (Pritchard) n. comb., P. citerovarium Martin, Cutmore & Cribb n. sp., P. hadrometra Martin, Cutmore & Cribb n. sp., P. heniochi Martin, Cutmore & Cribb n. sp., and P. ovatheculum Martin, Cutmore & Cribb n. sp. Given the diversity uncovered here and the ubiquity, abundance and diversity of butterflyfishes on coral reefs, we predict that Polypipapiliotrema will prove to comprise a rich complex of species causing disease in corals across the Indo-Pacific. The unique life-cycle of these taxa is consistent with phylogenetic distinction of the group and provides evidence for a broader basis of diversification among the family. We argue that life-cycle specialisation, in terms of adoption of disparate second intermediate host groups, has been a key driver of the diversification and richness of the Opecoelidae, the largest of all trematode families and the group most frequently encountered in coral reef fishes.     

Scent-marking in captive red pandas (Ailurus fulgens)

Three male and three female captive red pandas (Ailurus fulgens) were observed during and outside of the breeding season to examine changes in scent-marking behavior. Variation in scent-marking was analyzed with respect to site preferences, sex differences, onset of breeding, behavioral correlates, and environmental factors. Both males and females exhibited significant preferences for particular marking sites, those being prominent points in the enclosures. Males showed significantly higher scent-marking frequencies than females, except in one enclosure where increased marking behavior was associated with the presence of young. Sexual dimorphism in the pattern of marking was also observed, with males showing a bidirectional mark and females a unidirectional mark. Female marking was greater during the breeding season. Sniffing and number of waddles per mark were associated with scent-marking. Temperature change was not related to frequency of scent-marking. These results are compared with scent-marking behaviors in other species of carnivores and functional explanations are suggested.     

Marine phytoplankton at the Weddell Sea ice edge: Seasonal changes at the specific level

Summary The Antarctic ice edge acts as a dynamic frontal system on the phytoplankton in the water column. Austral spring and autumn cruises to the Weddell Sea ice edge provided the opportunity to compare phytoplankton at the beginning of biological spring and at the end of biological autumn. The USCGC icebreakers Westwind (1983) and Glacier (1986) went into the sea ice, and the RV Melville (1983 and 1986) completed the transects in the adjacent open ocean. Field samples were observed alive on board ship to record different lifestages near the ice edge. In both seasons cell numbers were low under the ice, and single cells or short chains were the common growth habit. In spring in the open ocean, long chains of vegetative cells with large vacuoles and gelatinous colonies of diatoms and of prymnesiophytes dominated; in autumn in the open ocean close to the accreting ice edge, short chains, single cells, and resting spores were mostly packed with storage products. Enlarged cell diameters and auxospores also occurred near the ice cover in the autumn. Species from the following genera are included: the diatoms Leptocylindrus, Stellarima, Thalassiosira, Eucampia, Corethron, and Chaetoceros, the prymnesiophyte Phaeocystis, and the chrysophyte Distephanus.     

Surface-core correlations in serum lipoproteins

It has been found that the capacity of lipoproteins for binding Mn(II) ions is dependent on the arrangement of the Iipoprotein core. A change in the molecular organization of the LDL core (thermotropic transition) is associated with the change on the lipoprotein surface. In HDL there is no thermotropic transition and no abrupt change of the binding capacity.. The observed surface-core correlation might be an important link in understanding how dietary fat influences the lipoprotein metabolism.