Enumeration and isolation of cellulolytic and hemicellulolytic bacteria from human feces.

The fibrolytic microbiota of the human large intestine was examined to determine the numbers and types of cellulolytic and hemicellulolytic bacteria present. Fecal samples from each of five individuals contained bacteria capable of degrading the hydrated cellulose in spinach and in wheat straw pretreated with alkaline hydrogen peroxide (AHP-WS), whereas degradation of the relatively crystalline cellulose in Whatman no. 1 filter paper (PMC) was detected for only one of the five samples. The mean concentration of cellulolytic bacteria, estimated with AHP-WS as a substrate, was 1.2 X 10(8)/ml of feces. Pure cultures of bacteria isolated on AHP-WS were able to degrade PMC, indicating that interactions with other microbes were primarily responsible for previous low success rates in detecting fecal cellulolytic bacteria with PMC as a substrate. The cellulolytic bacteria included Ruminococcus spp., Clostridium sp., and two unidentified strains. The mean concentration of hemicellulolytic bacteria, estimated with larchwood xylan as a substrate, was 1.8 X 10(10)/ml of feces. The hemicellulose-degrading bacteria included Butyrivibrio sp., Clostridium sp., Bacteroides sp., and two unidentified strains, as well as four of the five cellulolytic strains. This work demonstrates that many humans harbor intestinal cellulolytic bacteria and that a hydrated cellulose source such as AHP-WS is necessary for their consistent detection and isolation.     

Genetics of resistance to the African trypanosomes. VI. Heredity of resistance and variable surface glycoprotein-specific immune responses

The question of genetic linkage of parasite-specific immune responses to resistance to infection in experimental African trypanosomiasis was addressed. For this purpose, major histocompatibility complex-compatible resistant and susceptible inbred mouse strains and their F1 hybrid, F2 hybrid, and backcross offspring were infected with Trypanosoma brucei rhodesiense LouTat 1. Immunologic control of the first peak of parasitemia and survival times were the parameters measured. As we have reported previously (R. F. Levine and J. M. Mansfield, J. Immunol. 133:1564, 1984), B10.BR/SgSnJ mice are relatively resistant and controlled the growth of the infecting variant antigenic type (VAT) by mounting an antibody response to exposed epitopes of the variable surface glycoprotein (VSG). Fluctuating parasitemias resulting from sequential growth of different variable antigenic types occurred subsequently, and these mice died with a median survival time of 48 days. C3HeB/FeJ mice, relatively susceptible, did not control the infecting VAT and did not exhibit VSG-specific antibodies. These mice died with a median survival time of 22 days. The (B10.BR X C3H)F1 hybrids derived from crosses between resistant and susceptible mice all exhibited VSG-specific antibody responses and controlled the infecting VAT population. However, the median survival time of the F1 hybrids (24 days) was not significantly different from the survival time of the susceptible C3H parent. These findings demonstrate for the first time that antibody-mediated control of parasitemia is inherited as a dominant trait; that overall resistance, as measured by survival time, is inherited as a recessive trait (e.g., susceptibility is dominant); and that the two events segregate independently of one another. Further analyses of the inheritance of immunity and resistance (survival time) were made in which the F2 hybrid and backcross studies revealed that there are multiple genes controlling the VSG-specific antibody response as well as determining susceptibility. An extension of the present studies to a similar but non-major histocompatibility complex-mouse model system of resistance and susceptibility (C57BL/6J and C3H/HeJ mice, F1 hybrids, and 11 recombinant inbred B X H strains derived from them) was made in order to link the strain distribution patterns of known genetic markers with control of VSG-specific antibody responses or with control of susceptibility. Results of this study showed that resistance varied independently of the ability to control parasitemia with VSG-specific B cell responses.(ABSTRACT TRUNCATED AT 400 WORDS)     

Functional homologs of the Arabidopsis RPM1 disease resistance gene in bean and pea.

We showed that a bacterial avirulence (avr) gene function, avrPpiA1, from the pea pathogen Pseudomonas syringae pv pisi, is recognized by some, but not all, genotypes of Arabidopsis. Thus, an avr gene functionally defined on a crop species is also an avr gene on Arabidopsis. The activity of avrPpiA1 on a series of Arabidopsis genotypes is identical to that of the avrRpm1 gene from P.s. pv maculicola previously defined using Arabidopsis. The two avr genes are homologous and encode nearly identical predicted products. Moreover, this conserved avr function is also recognized by some bean and pea cultivars in what has been shown to be a gene-for-gene manner. We further demonstrated that the Arabidopsis disease resistance locus, RPM1, conditioning resistance to avrRpm1, also conditions resistance to bacterial strains carrying avrPpiA1. Therefore, bean, pea, and conceivably other crop species contain functional and potentially molecular homologs of RPM1.     

Genetic engineering of trees: progress and new horizons

Genetic engineering of trees to improve productivity, wood quality, and resistance to biotic and abiotic stresses has been the primary goal of the forest biotechnology community for decades. We review the extensive progress in these areas and their current status with respect to commercial applications. Examples include novel methods for lignin modification, solutions for long-standing problems related to pathogen resistance, modifications to flowering onset and fertility, and drought and freeze tolerance. There have been numerous successful greenhouse and field demonstrations of genetically engineered trees, but commercial application has been severely limited by social and technical considerations. Key social factors are costly and uncertain regulatory hurdles and sweeping market barriers in the form of forest certification systems that disallow genetically modified trees. These factors limit and, in many cases, preclude field research and commercial adoption. Another challenge is the high cost and uncertainty in transformation efficiency that is needed to apply genetic engineering and gene editing methods to most species and genotypes of commercial importance. Recent advances in developmental gene-based transformation systems and gene editing, if combined with regulatory and certification system reform, could provide the foundation for genetic engineering to become a significant tool for coping with the increasing environmental and biological stresses on planted and wild forests.     

Responses of the stomata of Aster tripolium to calcium and sodium ions in relation to salinity tolerance

In previous work, the stomata of the maritime halophyte Astertripolium L. were shown to close when NaCl concentrations risein the vicinity of the guard cells. Further studies have nowrevealed important effects of calcium on the ionic responsesof the stomata. When the guard cells were presented with KCl,Ca²⁺ suppressed opening in a manner similar to that which hasbecome familiar in other species such as Commelina communisL. However, in the presence of NaCl, Ca²⁺ had the opposite effect,reducing the closing response to NaCl. This pattern of behaviouris discussed in relation to known salt effects on membranes,but the underlying physiological basis remains obscure. A previous study led to the hypothesis that the closing responseof the stomata to Na⁺ ions may make an important contributionto the salinity tolerance of this species. Here we report thatincreasing supplies of Ca²⁺ ions reduce the effect of salinityon stomatal conductance in the whole plant as well as in theisolated epidermis. This finding is consistent with the wellestablished role of calcium in increasing resistance to salinity:in the presence of high calcium the plant can tolerate a greatersalt intake, and hence there is a reduced need for transpirationto be restricted by partial stomatal closure. Key words: Sodium, calcium, Aster tripolium, stomata, salinity tolerance     

Analysis of copia sequence variation within and between Drosophila species

The sequences of the 5' long-terminal repeat (LTR) and adjacent leader regions of 27 full-length copia elements isolated from natural populations of Drosophila melanogaster, D. simulans, and D. mauritiana are presented. Phylogenetic analyses indicate that although D. melanogaster copia elements are distinct from those of D. simulans and D. mauritiana, the elements of these latter two species are not distinguishable from one another. LTRs and adjacent 5' leader regions of elements isolated from D. simulans and D. mauritiana are structurally similar to one another and carry substantial deletional variation mapping to regions previously identified as being of potential importance for copia expression.      

Low resolution mapping around the flavivirus resistance locus (Flv) on mouse Chromosome 5

Although the phenomenon of innate resistance to flaviviruses in mice was recognized many years ago, it was only recently that the genetic locus (Flv) controlling this resistance was mapped to mouse Chromosome (Chr) 5. Here we report the fine mapping of the Flv locus, using 12 microsatellite markers which have recently been developed for mouse Chr 5. The new markers were genotyped in 325 backcross mice of both (C3H/HeJxC3H/ RV)F₁xC3H/HeJ and (BALB/cxC3H/RV)F₁xBALB/c backgrounds, relative to Flv. The composite genetic map that has been constructed identifies three novel microsatellite loci, D5Mit68, D5Mit159, and D5Mit242, tightly linked to the Flv locus. One of those loci, D5Mit159, showed no recombinations with Flv in any of the backcross mice analyzed, indicating tight linkage (<0.3 cM). The other two, D5Mit68 and D5Mit242, exhibited two and one recombinations with Flv (0.6 and 0.3 cM) respectively, defining the proximal and distal boundaries of a 0.9-cM segment around this locus. The proximal flanking marker, D5Mit68, maps to a segment on mouse Chr 5 homologous to human Chr 4. This, together with the previous data produced by our group, locates Flv to a region on mouse Chr 5 carrying segments that are conserved on either human Chr 4, 12, or 7, but present knowledge does not allow precise identification of the syntenic element.