Correlation between developmental status of obelia hydranths and direction of hydroplasmic streaming within their pedicels

Summary Photographic illustration of the several stages in the life cycle ofObelia hydranths, together with a correlation of these with the direction of hydroplasmic streaming within the pedicels is used to demonstrate the significance of the structural changes as expressions of developmental and metabolic activity. When developmental growth induces anabolism, the current of hydroplasmic granules is out into the growing part; when feeding activity provides materials for growth and maintenance, the current is alternately towards and away from the functioning animal; when senility induces catabolism, the current is away from the disintegrating organism as the resolved substance is removed; and when the ground is being prepared for new growth initiation by cytoplasmic reconstitution, there is no current and the hydroplasmic granules are quiescent. Thus there is, as would be expected, positive correlation between the developmental and metabolic activity of the hydranth, and the direction of hydroplasmic streaming within its pedicel.These observations were made at the Marine Experimental Station of the Institute, North Truro, Massachusetts, with aid from the Capt. L. D. Baker Estate of Boston and Wellfleet.     

Relay-ray way of hydroplasm movement in hydroid colonies

In this study, we continued the investigation of the distribution system of colonial hydroids in the course of its development, starting with its emergence during the planula metamorphosis and ending with the formed colony. The hydroplasmic stream system of two species of colonial hydroids—Perigonimus abyssi G.O. Sars, 1874, and Stauridia producta Wright, 1858—was studied. We found that the main principle by which hydroplasma moves in these colonies, which form no shoots, is the relay-race from one hydranth to another through a stolon fragment connecting them or it moves past the neighbouring hydranth to the next one, etc. We show that the efficiency of the conducting (distribution) system does not depend on the level of complexity of the colonial structure. The results of this study confirm the absence of general colonial processes of integration and self-regulation in hydroid polyps.     

Conservation of upstream regulators of scute on the notum of cyclorraphous Diptera

Bristles on the notum of many cyclorraphous flies are arranged into species-specific stereotyped patterns. Differences in the spatial expression of the proneural gene scute correlate with the positions of bristles in those species looked at so far. However, the examination of a number of genes encoding trans-regulatory factors, such as pannier, stripe, u-shaped, caupolican and wingless, indicates that they are expressed in conserved domains on the prospective notum. This suggests that the function of a trans-regulatory network of genes is relatively unchanged in derived Diptera, and that many differences are likely to be due to changes in cis-regulatory sequences of scute. In contrast, in Anopheles gambiae, a basal species with no stereotyped bristle pattern, the expression patterns of pannier and wingless are not conserved, and expression of AgASH, the Anopheles proneural gene, does not correlate in a similar manner with the bristle pattern. We discuss the possibility that independently acting cis-regulatory sequences at the scute locus may have arisen in the lineage giving rise to cyclorraphous flies.     

Mutational analysis of the MAL1 locus of Saccharomyces: identification and functional characterization of three genes

Summary Fermentation of maltose by Saccharomyces strains depends on the presence of any one of five unlinked MAL loci (MAL1, MAL2, MAL3, MAL4 or MAL6). Earlier mutational analyses of MAL2 and MAL6 containing strains have identified a single complementation group at each of these two loci. However complementation analysis between naturally occurring Mal^– Saccharomyces strains isolated from the wild demonstrated the presence of two complementation groups (designated MALp and MALg) at the MAL1, MAL3 and MAL6 loci. The available evidence suggests that the MALp gene is functionally equivalent to the complementation group identified by mutational analysis at the MAL6 locus and that this gene encodes a protein involved in the regulation of the coordinate induction of both maltase and maltose permease synthesis.In this paper we report the isolation, in a well characterized MAL1 strain, of 47 mutants unable to ferment maltose. All the mutants, with one exception, map at the MAL1 locus. These mal1 mutants, except for one, are recessive to MAL1 and fall into two major complementation groups. Evidence is presented that these two classes of mutants identify both a gene involved in the regulation of maltose fermentation (MAL1R) and a gene involved in maltose transport (MAL1T). We also report here the isolation of a temperature sensitive maltose nonfermenting mutant mapping at the MAL1 locus identifying a third gene (MAL1S) at this locus. The maltase synthesized by this mutant, when assayed in cell-free extracts, is significantly more thermolabile than the wild type enzyme. Our findings demonstrate that MAL1 is a complex locus comprising at least three genes: MAL1R, a gene involved in the coordinate regulation of the synthesis of maltase and maltose transport; MAL1T, a gene encoding a component of the maltose transport system; and MAL1S, a likely candidate for the structural gene for maltase.     

Analysis of DNAs from two species of the virilis group of Drosophila and implications for satellite DNA evolution

The DNAs from two virilis group species of Drosophila, D. lummei and D. kanekoi, have been analyzed. D. lummei DNA has a major satellite which, on the basis of CsCl equilibrium centrifugation, thermal denaturation, renaturation and in situ hybridization is identical to D. virilis satellite I. D. kanekoi DNA has a major satellite at the same buoyant density in neutral CsCl gradients as satellite III of D. virilis. However, on the basis of alkaline CsCl gradients, the satellite contains a major and a minor component, neither one of which is identical to D. virilis satellite III. By in situ hybridization experiments, sequences complementary to the major component of the D. kanekoi satellite are detected in only some species and in a way not consistent with the phylogeny of the group. However, by filter hybridization experiments using nick-translated D. kanekoi satellite as well as D. lummei satellite I and D. virilis satellite III DNAs as probes, homologous sequences are detected in the DNAs of all virilis group species. Surprisingly, sequences homologous to these satellite DNAs are detected in DNAs from non-virilis group Drosophila species as well as from yeast, sea urchin, Xenopus and mouse.     

Photosynthetic performance of cold-sensitive mutants of maize at low temperature

The virescent character is a genetic variant in pigmentation characterized by a delay in greening. Seedlings of the virescent mutants v1, v2, v3, v4, v13, v16, v18, v19 and v26 of maize exhibit chlorosis when grown at low temperature. Chlorotic leaves contain plastids that appear to have been arrested at an early stage of development. The results indicated that V16, V2, V3 and V4 loci control early stages of chloroplast development while V1, V13 and V19 may play a role at the end of development. The mutations in the V18 and V26 loci may control an intermediate step. At the pigment level, the virescent mutants of maize differ widely from analogous mutations existing in other plants. The mutations were characterized by a reduced amount of chlorophyll a and b (up to 100 times in v16) and chlorophyll a/b ratio above normal (up to 13.7 in v16). Lutein content was reduced in all mutants (less than 3% in v16 compared to wild type) but v13, while pigments of the xanthophyll cycle were found at higher levels in v1 and v13 (more than 10 and 90%, respectively). The v2, v3, v4, v16 and v18 mutants that are most depleted in β-carotene (36 times less in average than wild type) are also deprived in D1 and D2 polypeptides. Moreover, the v2, v3, v4, v16 and v18 mutants characterized by a lower accumulation in lutein are most depleted of light-harvesting complex II. All mutants possess a functioning, fully reversible, non-photochemical quenching mechanism. This is most developed in the v13 and v19 mutants (φ_n = 0.48 and 0.44, respectively). These two mutants also have a relatively high primary photochemical yield for photosystem II and a functioning photosystem I (φ_p = 0.23 and 0.39, respectively). The most interesting mutant is v13 that shows severe chlorosis and possesses the most effective non-photochemical quenching mechanism(s), which is thought to provide protection against excess photon absorption by photosystem II.     

Revision of three species of the genusDiaphanosoma Fischer, 1850

Material from the type localities was used for the revision of three species:Diaphanosoma mongolianum Uéno, 1938,D. chankensis Uéno, 1939 andD. dubia Manuilova, 1964. The first species was described from lake Dalai-nor in northern China,D. chankensis from lake Chanka situated on the border between USSR and China, north of Vladivostok, andD. dubia from the lake Bolon in the catchment area of the river Amur. Topotypes were compared with other populations and new synonymy suggested: previously describedD. birgei spp.lacustris Kořínek, 1981 is a synonym ofD. mongolianum, andD. orghidani Negrea, 1982 was synonymized withD. chankensis. All three species belong to a group without a separate flap on the ventral margin of the carapace.Diaphanosoma mongolianum is a palaearctic species with possibly close relationship to the New-World-speciesD. birgei Kořínek.D. chankensis is a poorly known species found in several lakes in the Far East and with a peculiar distribution in lakes along the lower river Danube and in the eastern part of the Carpathian Mountains in Roumania.D. dubia is so far restricted to Central, East, and Southeast Asia.     

On the measurement of shapes

We are here concerned with the functionf which assigns to each pointP of an object the numberf(P) which is the shortest distance fromP to the border. This function appears in various guises in diverse biological studies. The functionf(P) is itself a measure of shape—or more precisely, an infinite set of measures, one for each point (and hence, in view of its geometric definition, usually in a form inconvenient for use). Thus in this paper we sought a reasonable representative of this infinite set of measures, namely themean of the numbersf(P) asP ranges over all points of the entity. Computability studies are developed for various classes of shapes. For example, (1) the mean for a lamina bounded by a polygon circumscribable about a circle of radiusr isr/3; (2) the mean for a domain bounded by a polyhedron circumscribable about a sphere of radiusr isr/4. The transition from pointwise to piecewisef(P), especially in the non-convex case, requires working with inequalities.     

Nucleotide sequence of the fixABC region of Azorhizobium caulinodans ORS571: similarity of the fixB product with eukaryotic flavoproteins, characterization of fixX, and identification of nifW.

Summary The nucleotide sequence of a 4.1 kb DNA fragment containing the fixABC region of Azorhizobium caulinodans was established. The three gene products were very similar to the corresponding polypeptides of Rhizobium meliloti. The C-terminal domains of both fixB products displayed a high degree of similarity with the -subunits of rat and human electron transfer flavoproteins, suggesting a role for the FixB protein in a redox reaction. Two open reading frames (ORF) were found downstream of fixC. The first ORF was identified as fixX on the basis of sequence homology with fixX from several Rhizobium and Bradyrhizobium strains. The second ORF potentially encoded a 69 amino acid product and was found to be homologous to a DNA region in the Rhodobacter capsulatus nif cluster I. Insertion mutagenesis of the A. caulinodans fixX gene conferred a Nif^– phenotype to bacteria grown in the free-living state and a Fix^– phenotype in symbiotic association with the host plant Sesbania rostrata. A crude extract from the fixX mutant had no nitrogenase activity. Furthermore, data presented in this paper also indicate that the previously identified nifO gene located upstream of fixA was probably a homologue of the nifW gene of Klebsiella pneumoniae and Azotobacter vinelandii.     

Detection of a novel subspecies of Francisella noatunensis as endosymbiont of the ciliate Euplotes raikovi

Francisella are facultative intracellular bacteria causing severe disease in a broad range of animals. Two species are notable: Francisella tularensis, the causative organism of tularemia and a putative warfare agent, and Francisella noatunensis, an emerging fish pathogen causing significant losses in wild and farmed fish. Although various aspects of Francisella biology have been intensively studied, their natural reservoir in periods between massive outbreaks remains mysterious. Protists have been suspected to serve as a disguised vector of Francisella and co-culturing attempts demonstrate that some species are able to survive and multiply within protozoan cells. Here, we report the first finding of a natural occurrence of Francisella sp. as a protist endosymbiont. By molecular and morphological approaches, we identified intracellular bacteria localized in a strain of the marine ciliate Euplotes raikovi, isolated from the coast of Adriatic Sea. Phylogenetic analysis placed these endosymbionts within the genus Francisella, in close but distinct association with F. noatunensis. We suggest the establishment of a novel subspecies within F. noatunensis and propose the cytoplasmatic endosymbiont of E. raikovi as “Candidatus F. noatunensis subsp. endociliophora” subsp. nov.     

Molecular characterization of an adenylate cyclase gene of the cyanobacterium Spirulina platensis

A cyaA gene, encoding an adenylate cyclase, was isolated from a filamentous cyanobacterium, Spirulina platensis, by functional complementation of a cya mutant of Escherichia coli, defective in adenylate cyclase activity. The predicted gene product of cyaA contains a signal peptide-like domain, a putative sensor domain similar to the gene product of vsrA of Pseudomonas solanacearum, a putative membrane-spanning domain and an adenylate cyclase-like catalytic domain. Two other positive clones that complemented the E. coli mutant were isolated from the same cyanobacterium, suggesting that several cya genes are functioning in S. platensis.     

The Evolution of RecD Outside of the RecBCD Complex

The common understanding of the function of RecD, as derived predominantly from studies in Escherichia coli, is that RecD is one of three enzymes in the RecBCD double-stranded break repair DNA recombination complex. However, comparative genomics has revealed that many organisms possess a recD gene even though the other members of the complex, recB and recC, are not present. Further, bioinformatic analyses have shown that there is substantial sequence dissimilarity between recD genes associated with recB and recC (recD1), and those that are not associated with recBC (recD2). Deinococcus radiodurans, known for its extraordinary DNA repair capability, is one such organism that does not possess either recB or recC, and yet does possess a recD gene. The recD of D. radiodurans was deleted and this mutant was shown to have a capacity to repair double-stranded DNA breaks equivalent to wild-type. The phylogenetic history of recD was studied using a dataset of 120 recD genes from 91 fully sequenced species. The analysis focused upon the role of gene duplication and functional genomic context in the evolution of recD2, which appears to have undergone numerous independent events resulting in duplicate recD2 genes. The role of RecD as part of the RecBCD complex appears to have a divergence from an earlier ancestral RecD function still preserved in many species including D. radiodurans.     

Reaction of Diaporthe longicolla to a strain of Sarocladium kiliense

Phomopsis seed decay of soybean [Glycine max (L.) Merr.] is a seedborne fungal disease caused by Diaporthe longicolla that causes yield losses and reduced seed quality. Biocontrol of this pathogen by a strain of Sarocladium kiliense isolated from a culture of D. longicolla was investigated in vitro and in vivo. A zone of inhibition formed between the two fungi in vitro, but was poorly sustained, and inhibition of conidial germination of D. longicolla by a culture filtrate of S. kiliense was not significant, though D. longicolla mycelial growth was inhibited by a 25% culture filtrate. Co-inoculation of both fungi failed to reduce seed rot or increase seed germination in greenhouse and growth chamber experiments, respectively. Co-inoculation of both fungi also failed to reduce pycnidial development in colonies of D. longicolla growing on leaf pieces, but soaking of the leaf pieces with S. kiliense conidia for one or three days prior to inoculation with D. longicolla eliminated pycnidial development completely. Although it was not possible to reproduce the parasitism of S. kiliense on D. longicolla under the experimental and environmental conditions used, the potential to use S. kiliense as a protectant biocontrol for soybean fungal pathogens should be further investigated.     

Seasonal study of the fungal biota of the fur of dogs

During a one year period, 944 dogs from the Municipal kennel of Barcelona were examined to detect animals with suspected dermatophytosis. Only a few animals (1.8%) presented skin lesions but none of them had dermatophytosis. A representative number of dogs without visible skin lesions (n=172), selected at random, were used to carry out a seasonal study of the mycobiota of their fur. Fifteen isolates belonging to the genera Microsporum and Trichophyton were isolated from 14 of the 172 (8.1%) dogs without lesions. The identity of these fungi was Microsporum gypseum (6/15), Trichophyton terrestre (4/15), M. canis (2/15), M. cookei (2/15) and Trichophyton ajelloi (1/15) (one strain each of M. gypseum and T. ajelloi were isolated from one dog). Species of Penicillium (% prevalence=89.5%), Alternaria (86.6%), Cladosporium (84.9%), Aspergillus (77.3%), Scopulariopsis (65.7%) and Chrysosporium (64.5%) were the most prevalent. No significant differences in the fungal biota were observed with respect to age, gender, hair length or between mixed and pure breed dogs. A large number of isolates, including species belonging to the genera Beauveria, Chrysosporium, Malbranchea and Scopulariopsis, that macroscopically and/or microscopically resemble dermatophytes and may be mistaken for them, produced a red color change in Dermatophyte Test Medium. No significant seasonal difference was detected among the isolates belonging to the the most frequently encountered genera, with the exception of Scopulariopsis (higher in summer and autumn) and Chrysosporium (higher in summer). Species from other genera, with lower occurrence also presented significant differences in their seasonal distribution. Arthrinium, Aureobasidium, Chaetomium and Phoma spp. presented maximum prevalence peaks in spring, Fusarium, Paecilomyces, Phoma and Rhizopus spp. in summer and Geotrichum and Mucor spp. in autumn. The Microsporum and Trichophyton species were more frequently isolated in summer.     

Estimation of Fractional Turnover Rate of Aldolase in Skeletal Muscle of the Adult Rat by Simultaneous Administration of Glutamic Acid-1 -14C and Glutamic Acid-3-3H

The spc operon of Escherichia coli encodes 11 ribosomal proteins and SecY. The secY gene and downstream rpmJ encoding a ribosomal protein, L36, are located distal to the promoter of the spc operon. It has been suggested that the stability of SecY mRNA depends on rpmJ unless a ρ-independent terminator is inserted immediately downstream of secY. Moreover, it has been suggested that RpmJ is dispensable for E. coli. We constructed rpmJ null strains, AY101 (ΔrpmJ::tetA) and AY201 (ΔrpmJ::cat), by replacing rpmJ with tetA, which encodes a membrane protein responsible for tetracycline-resistance, and cat, which encodes a cytoplasmic chloramphenicol acetyltransferase, respectively. Depletion of RpmJ did not inhibit protein synthesis, whereas the growth of AY101 was defective at high temperatures. The level of SecY mRNA decreased significantly in both disruptants even though the ρ-independent terminator was inserted immediately downstream of secY. Some periplasmic proteins were missing in the disruptants with a concomitant increase in the amount of phage shock protein in the inner membrane. These phenotypes caused by the rpmJ null mutation were corrected by a plasmid carrying secY, but not by one carrying rpmJ.