Genetics of Ethanol-Producing Microorganisms

Abstract

Ethanol-Producing Microrganisms

A wide variety of microbial species are known to produce ethanol as a product of carbohydrate fermentation.¹ Organisms which have received attention in recent studies include a wide range of yeasts, some molds, and a number of specialized bacteria (Table 1). Traditionally, yeasts, particularly Saccharomyces cerevisiae, have been used for producing fermentation ethanol or alcoholic beverages in large-scale processes. In Table 1, Zymomonas mobilis, the predominant organism in fermentations producing Mexican “pulque” or palm wine,³⁴-⁴⁶ is the only bacterium of current economic significance. However, the development of interest in other species with the ability, for example, to convert xylose to ethanol or to ferment at high temperatures indicates that no existing strain of Saccharomyces or Zymomonas meets the specifications for all current and future uses. Certainly the use of alternative organisms, or even mixed cultures,⁴²⁴⁵ warrants investigation. However, this review will concentrate on proven ethanol producers (i.e., yeasts, particularly Saccharomyces spp., and Z. mobilis) and how these might be improved in a systematic way for ethanol production, using the wide range of genetic techniques which is now available.     

Algebraic Methods in Evolutionary Genetics

This paper is a survey of some results obtained in evolutionary genetics by algebraical methods. The main topics: 1. Some special classes of algebras which arising in population genetics (stochastic, baric, BERNSTEINian, genetic etc.). 2. The BERNSTEIN'S problem and the stationary genetic structure. 3. The convergence to an equilibrium, the rate of convergence. 4. The exact linearization of evolutionary equation. 5. The exact formulae for evolutionary spectrum and for solution of the evolutionary equation.     

Evolutionary Genetics of Animal Migration

Three primary approaches have been used to study the geneticsof migration: the analyses of population differences, of singlelocus effects, and of polygenic influences. Studies of populationsreared under similar conditions in "common garden" experimentsfrequently reveal gene effects contributing to differences inmigratory tendency. Single locus effects are known, but arenot common, a result to be expected given that migration iscomplex. Quantitative genetic studies reveal that heritabilitiesfor migration related traits are often high (approximately 0.5or more) suggesting significant amounts of genetic variationon which natural selection can act. Analyses of genetic correlationsdemonstrate that migratory behavior is part of a syndrome thatincludes aspects of both physiology and life history traits.The latter are characteristically those which contribute tocolonizing ability. Migratory behavior thus does not evolvein isolation. New migration patterns are still evolving, aswould be predicted from observed environmental changes and thegenetic variation present in migratory species.     

Evolutionary Genetics of Drosophila Mediopunctata

Drosophila mediopunctata belongs to the tripunctata group, which is the second largest Neotropical group of Drosophila with 64 species described. Here I review the work done with this forest dwelling species, and some applications of the methods developed using it as a model organism, to other species. Specifically I look at: the phylogenetic status of the tripunctata group and its relation with other groups in the Hirtodrosophila-immigrans radiation; D. mediopunctata’s chromosome inversion polymorphism (altitudinal cline of frequencies and evidences of selection); the morphological variation of the wing and the development and applications of the ellipse method to describe the morphology of the wing; the variation on the number of aristal branches; the genetic basis of the polychromatism present in D. mediopunctata and its association with chromosome inversions; the sex-ratio trait and its use in the demonstration of Fisher’s principle; and, finally, the finding of the transposable P-element in this species. This paper is respectfully dedicated to Prof. Sergio Olavo Pinto da Costa whose help was decisive in the initial stages of our work.     

微重力和宇宙射线对某些微生物的影响

随着科学的发展,人造卫星的发射成功,人类开始迈向空间,为揭示太空的真实情况,国内、外学者已进行了大量的探索工作(鲁子贤 1988)。我们利用我国发射的人造卫星进行了搭载试验。本文报道空间环境对微生物生长与遗传性状影响的     

Evolutionary Genetics of Nodule Bacteria: Molecular and Population Aspects

The molecular analysis of the genetic systems controlling the main stages of nodule bacteria (rhizobia) interaction with a legume host (signaling at early stages and symbiotic nitrogen fixation) has shown that the widespread recombination of genetic material in free-living ancestors of rhizobia was an important factor in the evolution of these systems. These recombinations could be conditioned by a high content of repeated DNA sequences and the IS elements in the rhizobial genome. A high recombination activity of rhizobia is manifested in the panmictic structure of their populations, which is associated with frequency-dependent selection favoring rare recombinants. This selection is realized through the competition of virulent strains for the nodule formation and can be controlled by the genes whose expression depends on population density (via the quorum sensing mechanism). A high degree of panmixia in rhizobial populations is associated with their ecotypic polymorphism, manifested as the coexistence of symbiotic and nonsymbiotic strains. This type of polymorphism is caused by individual selection during the periodic changes of ecological niches (soil–plant host) in the rhizobia life cycle. The rhizobia–plant interaction stimulates selection in bacterial populations, which results in the increased levels of their heterogeneity and panmixia. The combination of individual and frequency-dependent selection types resulted in the high rates of symbiosis evolution and polyphyletic origin of diverse rhizobial species.     

Pattern Formation in Cluster Roots: Some Developmental and Evolutionary Considerations

Cluster roots, also known as proteoid roots, are one of themajor adaptations for nutrient acquisition in terrestrial vascularsporophytes, occurring in many important plant families, inkey areas of biodiversity, and in significant ecological niches.Their development and function are closely linked and presentan ideal experimental system with which to investigate the basisof pattern and its morphogenetic amplification. Both meristemfunction and root initiation are controlled within a spatialand temporal framework, resulting in predictive phenotypic expression.In this paper, these patterns of development are described withinthe context of our knowledge of lateral root initiation anddevelopment. Recent work is summarized in an attempt to highlightthe issues of most importance for future research. The caseof the genus Lupinus is taken as a means of exploring the phylogeneticrelationships of species with cluster roots. The first evidenceof cluster roots having arisen only once within the Lupinusgenus is presented. Copyright 2000 Annals of Botany Company Cluster root, development, lateral root, lupin evolution, nutrient acquisition, pattern, proteoid root     

Synergistic Actions of Halogenophenols on Radiation Inactivation of Microorganisms

The combined effects of radiations and halogenophenols were investigated. The activities of these reagents to increase the radiolethality during irradiation were demonstrated with E. coli and Z. soya. Some relationships between chemical structure and activity were revealed as follows at pH 6 and 8: (1) effectiveness of substituted halogen was in the order of I>Br>Cl; (2) effectiveness of the monosubstituting position on a benzene ring of halogenophenols was increased in the order of p->m->o-; (3) effectiveness increased with increasing the number of halogen atom. The halogenophenol action was also found to be considerably pH-dependent. In the case of chlorinated derivatives, the synergistic activity to increase the radiolethality was intensified on the acidic side, though bromides and iodides were more effective on the basic side.