Mixing time in airlift reactors during citric acid fermentation

Citric acid fermentations using strain Aspergillus niger were carried out in three airlift reactors of volumes of 10, 35 and 200 liters. Mixing times were measured at the beginning and the end of fermentation. It has been shown that the mixing time at the end of fermentation is approximately equal to the duration of one circulation period. This was due to the flow regime transition caused by the change of rheological properties of the mould broth during fermentation.     

Uncultivated Foods in Southern Veracruz,Mexico: Establishing the Links between Ecosystem Health,Food Availability,and Human Nutrition

Uncultivated foods have received little attention in the scientific literature and nutrition programs of Mexico because they are usually seen as complementary to agricultural activities, i.e., corn planting and harvesting. Using an ecosystem approach to human health, this article examines the availability, nutritional contribution, and consumption patterns by gender and age of such foods in Ixhuapan and Ocozotepec, two native communities of southern Veracruz, Mexico. The research shows important differences between both communities. Ixhuapan has a more uniform environment and its people have opted for commercial activities and land parceling. Land use changes have led to a decrease in the number of people engaged in subsistence agriculture, environmental degradation, lower corn yields, and the loss of traditional, uncultivated foods. These changes have had a negative impact on the nutritional status of Ixhuapan children and adults, particularly women. Within each community, however, there are also important differences in terms of access to resources based on gender and age. Men catch game and large fish while women catch shrimp. Men gather seasonal plants in the forest while women gather wild weeds in the cornfields and spices in their backyards. Boys, more often than girls, obtain fruits from trees located in their backyard or the town’s public spaces. The article shows that women’s food resources are frequently consumed and constitute good sources of micronutrients.     

Nuclear microsatellite loci for Arabidopsis halleri (Brassicaceae), a model species to study plant adaptation to heavy metals

? Premise of the study: Arabidopsis halleri is a model species to study the adaptation of plants to soils contaminated by zinc, cadmium, and lead. To provide a neutral genetic background with which adaptive genetic markers could be compared, we developed highly polymorphic neutral microsatellite markers. ? Methods and Results: Using a microsatellite-enriched library method, we identified 120 microsatellite loci for quantitative trait locus (QTL) mapping analysis, of which eight primer pairs were developed in a single multiplex for population genetic studies. Analyses were performed on 508 individuals from 26 populations. All loci were polymorphic with six to 23 alleles per locus. Genetic diversity varied between 0.56 and 0.76. ? Conclusions: Our results demonstrated the value of these eight microsatellite markers to investigate neutral population genetic structure in A. halleri. To increase the resolution of population genetic analyses, we suggest adding them to the 11 markers previously developed independently.     

Vibratory signals of four Neotropical stink bug species

Abstract. The stink bugs Acrosternum impicticorne, Euschistus heros, Piezodorus guildinii and Thyanta perditor (Heteroptera: Pentatomidae) feed and mate on the same host plants and constitute major components of the soybean pest complex in Brazil. During mating, they communicate with species and sex-specific vibratory signals whose spectral properties are characteristic of the subfamily Pentatominae. Songs differ between species in the time structure and amplitude modulation of their units. The repertoire of A. impicticorne, E. heros and T. perditor fits into the scheme described for most investigated stink bugs: females call with a sequence of pulses that differ between species in their duration and repetition rate, and males respond with courtship songs of species-specific temporal structure and amplitude modulation of complex pulse trains. Female calling and male courtship songs are the main constituents of vibratory communication between sexes in the mating period. The other vibratory emissions appear to represent either transitional songs, support recognition during close-range courtship, or are involved in male rivalry. The first recorded vibratory emissions of P. guildinii confirm that the genus Piezodorus represents an exception within the Pentatominae. Irregularly repeated female vibratory signals of P. guildinii do not trigger typical male courtship responses as they would in the small stink bugs Holcostethus strictus and Murgantia histrionica. On the other hand, complex rivalry with extensive frequency modulation of pulses, as also described in Piezodorus lituratus, opens a new insight into the role of vibratory communication in stink bugs.     

Characterization and disruption of exonuclease genes from <Emphasis Type="Italic">Streptomyces aureofaciens</Emphasis> B96 and <Emphasis Type="Italic">S. coelicolor</Emphasis> A3(2)

Streptomyces aureofaciens B96 produces several intra- and extracellular enzymes with deoxyribonuclease activity. According to the sequence of the previously published gene exoSc from S. coelicolor A3(2), the DNA sequence from S. aureofaciens B96 was amplified, cloned and expressed in E. coli. The protein product of exoSa gene, recExoSa, was also an exonuclease with DNAase and 5′-phosphomonoesterase activities at optimum temperature 37 °C and pH 8.0. It degraded only linear DNA (chromosomal, double-stranded and single-stranded) and linear plasmid DNA from both ends, with a preference to blunt ends in comparison with overhang ends. The purified enzyme exhibited no RNAase activity. Both exoSc and exoSa genes were interrupted by the apramycin resistance gene; constructed fragments were transformed into particular streptomyces protoplasts. Mutation caused by exoSa disruption in S. aureofaciens chromosome and mutation by interrupted exoSc in S. coelicolor were lethal.     

Streptomyces aureofaciens strains as hosts for cloning of genes affecting antibiotic production

Summary Several mutants ofStreptomyces aureofaciens strain were used for protoplast regeneration and plasmid transformation. All tested mutants (excepting R 8/26) were transformable by number of plasmids and shuttle vectors. The transformation of the CTC production strains by plasmid containing cloned CTC resistance gene resulted in 1,1–4 times higher antibiotic production. From the restriction analysis of plasmid, phage and chromosomal DNAs it was estimated, that all tested mutants normally contain the modification system analogous toNae I (Roberts, 1987). Mutant R 8/26 expresses not only complete restriction-modification system mentioned above but also potential second system restricting several actinophages.     

Antibodies against Leptospira interrogans in California sea lion pups from Gulf of California

One hundred and twenty-five serum samples from California sea lion (Zalophus californianus californianus) pups, and one from an adult female from eight reproductive rookeries located in seven islands in the Gulf of California (Mexico), were collected during the 1994-96 reproductive seasons. These were tested for antibodies to 19 serovars of Leptospira interrogans using a Microscopic Agglutination Test (MAT). Forty-one samples (32%) had antibody levels from 1:20 to 1:320 to one or more serovars. The most frequently detected serotypes were Leptospira interrogans hardjo (n = 13), cynopteri (8), ballum (6), and szwajizak (5). Serovars with the highest prevalence were Leptospira interrogans hardjo and serjoe (1:320), ballum (1:160), and cynopteri, girppotyphosa, and tarassovi (1:80). Based on these results, exposure of sea lions to L. interrogans serovar hardjo seems to be relatively common among colonies located in the islands of the Gulf of California in contrast with those located on the Pacific coast, where the most frequently detected serovar is L. interrogans serovar pomona.     

The use of comparative genome analysis and syntenic relationships allows extrapolating the position of Zn tolerance QTL regions from Arabidopsis halleri into Arabidopsis thaliana

Arabidopsis halleri is a species that has undergone natural selection for zinc (Zn) tolerance. Isolation of the quantitative trait loci (QTL) associated with this trait holds great promise for the identification of the main genes responsible for this adaptation. Using a segregating progeny produced by an interspecific cross, we previously constructed a genetic linkage map of A. halleri × A. lyrata petraea and mapped the three main QTL that confer Zn tolerance in A. halleri (Willems et al.). The goal of the present study is to compare the genetic linkage map of A. halleri × A. l. petraea to the annotated A. thaliana genome sequence to generate a tool for A. halleri genomic approaches. To achieve this aim, we constructed a genetic linkage map with 81 markers anchored on A. thaliana, including 23 genes known to be involved in metal homeostasis. First, this provided an extensive overview of the chromosomal rearrangements that have occurred since the divergence between A. thaliana and its closest relative A. halleri. Second, on the basis of the syntenic relationships assessed experimentally through this work, we transferred the QTL confidence intervals for Zn tolerance to the A. thaliana physical map, allowing access to all the genes localized in the corresponding regions. Third, we validated from the 23 genes involved in metal homeostasis the three ones localized in the QTL regions that can be considered the best candidates for conferring Zn tolerance. Nancy H. C. J. Roosens and Glenda Willems contributed equally to this paper.     

Proposal for the Establishment of the Core Zones in the Biosphere Reserve of Tehuacán-Cuicatlán, Mexico

This work proposes the establishment of core zones in the Biosphere Reserve of Tehuacán-Cuicatlán (BRTC), based on plant species richness and endemism. A total of 561 species of the four most important plant families in the region (Asteraceae, Cactaceae, Leguminosae and Poaceae) as well as 174 endemic species of these and other families were used in the analyses. Distribution of these taxa was analyzed using two different iterative complementarity methods. Significant correlations were found between patterns of species richness and endemic plants distribution in the study area. These results were combined with other analysis where two different indices (species richness index and human population index) were used. The results suggest the delimitation of four core zones within the Biosphere Reserve, covering a total area of 105,300 ha. The core zones represent 21.8% of the area, and would protect 72.54% of the species from the selected plant families and 67.8% of endemic species.     

Characterization of a complex restriction-modification system detected in<Emphasis Type="Italic">Staphylococcus aureus</Emphasis> and<Emphasis Type="Italic">Streptococcus agalactiae</Emphasis> strains isolated from infections of domestic animals

Characterization of classic type II restriction-modification systems (RMS) (restriction endonucleases and modification methyltransferases) was carried out in isolates ofStaphylococcus aureus andStreptococcus agalactiae obtained from clinical material. Among the 100 isolates ofS. aureus two different RMS type II were detected. The first was expressed in isolates 32 and 33 (Sau32 I andSau33 I); the targeting sequence was determined as 5′-GGN CC-3′ (Sau96 I isoschizomer). The second was found in isolates no. 90, 93, 96*, and 98 (Sau90 I,Sau93 I,Sau96* I,Sau98 I) and enzymes recognized sequence 5′-CTY RAG-3′ (SmlI isoschizomer). Analysis of 40 isolates ofS. agalactiae revealed only one RMS; it was detected in two isolates (no. 16 and 23;Sag16 I andSag23 I). Restriction endonuclease expressed by these isolates cleaved DNA in sequence 5′-CTG CA/G-3′ (PstI isoschizomer). In RMS-positiveS. aureus andS. agalactiae isolates plasmid DNA capable of replication inEscherichia coli andBacillus subtilis was also detected and isolated. This research was supported by VEGA grant of theSlovak Academy of Sciences no. 2/2059/22 and grant no. 2003 SP27/0208E 02/028/0E02 of theMinistry of Agriculture of the Slovak Republic.