An analysis of the organization and evolution of type 4 fimbrial (MePhe) subunit proteins

Summary We have analyzed and compared the amino acid sequences of the type 4 fimbrial subunits fromPseudomonas aeruginosa, Moraxella bovis, M. nonliquefaciens, Bacteroides nodosus, Neisseria gonorrhoeae, andN. meningitidis. We propose a consensus sequence for the highly conserved aminoterminal regions of these proteins. In the variable regions, a domain corresponding to an epitope common toN. gonorrhoeae andN. meningitidis fimbriae is conserved, both in sequence and in environment, in fimbrial subunits fromB. nodosus. The subunits fromM. bovis andP. aeruginosa do not show any homologies to this sequence. In all of the subunits, the carboxy-terminal half of the molecule consists of a series of fairly hydrophobic domains. The last three domains, two of which include the cysteines of the disulfide bridge inN. gonorrhoeae, P. aeruginosa, andM. bovis, are more or less conserved in sequence in all of the proteins including that ofB. nodosus. We propose that these conserved hydrophobic regions, which have the potential to form a series of beta-sheets, form a structural framework around which more variable hydrophilic sequences determining immunological profile are arranged. The evolutionary relationships of the contemporary proteins and the distribution of type 4 fimbriae are also discussed.     

Obligately phototrophic Chloroflexus: primary production in anaerobic hot spring microbial mats

Microbial mats which lack cyanobacteria occur at 50° to 65° C in the sulfide-containing Mammoth Springs of Yellowstone National Park. The principal organisms within these mats are filamentous bacteria which resemble Chloroflexus aurantiacus. The incorporation of [¹⁴C]-HCO ₃ ^- into mat material depended upon both light and sulfide, and was not inhibited when complete natural light was replaced with far-red and infra-red radiation. [¹⁴C]-acetate was incorporated in a light-dependent reaction which was stimulated by, but did not require, sulfide. In situ experiments with microelectrodes demonstrated net sulfide uptake by the mat in the light, and net sulfide production by the mat in the dark, suggesting the operation of a sulfur cycle.Filamentous phototrophic bacteria isolated from the mat were incapable of sustained growth in the presence of O₂.Simultaneous exposure of cultures to light and O₂ caused degradation of bacteriochlorophyll c. The stimulation of light-dependent [¹⁴C]-HCO ₃ ^- -uptake by sulfide was more pronounced in these isolates than in strains of Chloroflexus aurantiacus.     

Root and microbial biomass dynamics under the canopy of the desert shrub Zygophyllum dumosum

Summary A study was done to evaluate the influence of soil moisture and rainfall on root and microbial biomass production under the canopy of the desert shrub Zygophyllum dumosum. During the study period the root biomass production increased following the early rains but subsequently declined, remaining fairly constant thoroughout the season. In contrast microbial biomass and soil organic matter increased during the rainy season and declined with the onset of the dry summer period. Based on our results we suggest that the moisture event and not the amount and the organic matter content regulate root and microbial biomass production at the 0 to 10 cm soil layer.Contribution of the Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel. paper no. 2617-E, 1989 series     

Effects of microbial floras on the distributions of five domestic Drosophila species across fruit resources

Summary The distributions of five Drosophila species and four components of the microflora have been compared across a total of 48 traps baited with four different fruit and vegetable substrates in two domestic compost heaps in Canberra (Australia). Large and consistent differences are found, both among the Drosophila and among the microbial classes, in their distributions across traps baited with different substrates. Moreover the distribution of each Drosophila species shows a unique set of strong associations with the microbial distributions. Thus the distributions of both D. simulans and D. melanogaster are found to be strongly negatively correlated with the abundance of bacteria while D. simulans is also strongly positively correlated with the titre of fermenter yeasts. D. immigrans is strongly positively correlated both with bacteria and with non-fermenter yeasts. D. hydei is positively correlated with nonfermentery yeasts and D. busckii is negatively correlated with fermenter yeasts. Moulds are the only microbial class not consistently associated with the distribution of any of the Drosophila species. The correlations with the other microbial classes are sufficient to explain the majority of the abundance differences of the Drosophila species among the trap types. It is therefore proposed that the clear partitioning of the fruit resources by the Drosophila is due to their differing primary interactions with the microflora.     

Growth and turnover of microbial biomass during the decomposition of organic matter(Polygonum cuspidatum) in vitro

Air-dried fresh and dead specimens ofPolygonum cuspidatum were incubated for 250 days in the laboratory, and the growth and turnover of microbial biomass-C in the organic matter were studied. The biomass-C in the fresh leaf and fresh stem attained maximum levels on day 14 and day 7, respectively, and then settled down to stable levels. In the dead leaf and dead stem, increase in biomass-C ceased by day 4 and the biomass-C levels did not change thereafter. The turnover time of the biomass-C was estimated from the amount of biomass-C and the release rate of CO₂-C. The turnover was rapid in the early period of incubation. Then the turnover time became longer and after incubation for 70 days the values approached those in natural soils (longer than 16 days). During the incubation period, nitrogen was not mineralized in any organic matter. In the dead leaf and dead stem, asymbiotic nitrogen fixation activity increased after incubation for about 40 days and disappeared by the end of the incubation period, whereas nitrogen fixation was hardly detected in the fresh leaf and fresh stem.     

水洞沟遗址的环境与地层

水洞沟第四纪地层可与萨拉乌苏河组上段对比。水洞沟遗址包含有新石器和旧石器晚期文化,其旧石器晚期文化发生在距今20,000多年至10,000多年间的黄土状粉砂土中,即发生在末次冰期主冰期的干冷环境下,比发育在距今约35,000—50,000年间的萨拉乌苏河旧石器文化为晚。     

Experimental formulations ofBacillus sphaericus for the control of anopheline and culicine larvae

Summary Four experimental formulations ofBacillus sphaericus Neide (2362 isolate) were evaluated for larvicidal activity against culicine and anopheline larvae in several natural and artificial habitats. A granular formulation (5% primary powder) was tested against natural populations of mosquitoes in two simulated habitats in Florida and in maturing and reflooded rice fields in Louisiana. Larvae ofCulex quinquefasciatus Say were reduced by 97 and 99% after application of the granules at the rate of 10 kg/ha to polluted tanks and 2.5 kg/ha to sod-lined potholes, respectively. Anopheline andPsorophora columbiae (Dyar and Knab) larvae were reduced by 68 and 92–100%, respectively, after application of 5 kg granules/ha to rice fields. A flowable concentrate (12.8% primary powder) applied to unpolluted and organically enriched habitats in Florida at 0.25 kg/ha reduced populations ofCulex spp. by 93–100% and 99%, respectively. Sustained-release briquets (5% primary powder) applied at the rate of one half briquet/1.8 m² sod-lined potholes reduced larval populations ofCx. quinquefasciatus by 88–95% for up to 2 weeks in open sunlight. Sustained-release pellets (30% primary powder) applied to small woodland pools in Memphis, TN at the rate of four pellets/pool virtually eliminated larval populations ofCx. restuans Theobald for over 8 days. Variable persistance of larvicidal activity was noted for the other treatments depending on the formulation, target species and habitat.     

Huge increase in bacterivores on freshly killed barley roots

Abstract Adding fresh roots to intact soil cores resulted in marked increases in microbial and microfaunal activity at the resource islands. Microbial activity increased in two phases following root addition. Respiratory activity and concentration of respiratory enzyme (dehydrogenase) in soil adhering to the roots was very high during the first three weeks resulting in anaerobic conditions in the soil. After a period of low respiratory activity and enzyme content, these quantities increased from 6 to 20 weeks, but not enough to maintain anaerobic conditions. Numbers of protozoa peaked earlier than the nematodes. Based on yield coefficients of microbes and bacterivores, the increase in bacterivores was in accordance with root-induced respiration activity. In soil adhering to roots, numbers of bacterial grazers (protozoa and nematodes) were up to 80 and 30 times higher, respectively, than in the surrounding soil. This effect is up to 20 times higher than observed around live root systems, which may suggest that the rhizosphere effect on microbivores could for the major part result from the decomposition of dead segments of the root system.     

Principal-components analysis of Brazilian Indian anthropometric data

Analysis of nine characteristics on 1,205 males and 932 females from 12 tribes or groups of tribes indicated a poor relationship between morphology and language, as well as moderate agreement with the variability expected considering geography only. Two samples in the Xingu area studied during an interval of half a century (1897-1947) showed remarkable similarity. The conformity of the Caingang morphology with those of other tribes and the distinctiveness of the Xavante and Tenetehara has been amply confirmed.     

Ecology of nematophagous fungi: vertical distribution in a deciduous woodland

Summary The distribution of nematophagous fungi in soil collected from a deciduous woodland is compared to various biotic and abiotic soil factors. The microfungi are isolated at all depths down to a maximum of 35 cm. Predators forming constricting rings, adhesive branches and adhesive knobs are restricted to the upper litter and humus layers. The net forming predators and endoparasites are isolated at all depths, although they are significantly more abundant in the lower mineral rich soils. A much greater species diversity of nematophagous fungi is recorded in the upper organic zones.Preliminary soil analysis indicates thatCephalosporium balanoides is independent of all soil variables, while predators able to form traps spontaneously are restricted to the organic soils which are rich in nematodes. Non-spontaneous trap forming predators, which are excellent saprophytes, are isolated from the deeper soils which are low in nutrients. The ecological significance of these results is discussed.