Genetic and evolutionary consequences of symbiosis

Permanent stable symbioses, primarily microbial, are analyzed as parasexual phenomena from the evolutionary point of view. Such associations bring together in single individuals heritable traits of high selective advantage in certain environments. By convergent evolution several types of associations have repeatedly arisen: motile photosynthetic forms, nitrogen fixing and wood digesting complexes, and so forth. Many examples are discussed from the point of view of the number of originally independent genomes that comprise the recognizable individuals.The level of partner integration in many associations is analyzed. Examples of many levels: genic, gene product, metabolite, behavioral, and the methods by which they can be distinguished are discussed.The literature concerning a large number of associations is reviewed: Methanobacillus; predatory and consortia bacteria; blue green algal sheath dwelling bacteria; anaerobic worm-bacterial; algal, and foreign chloroplast retention by heterotrophic eukaryotes (ciliates, coelenterates, mollusks); the double nucleated photosynthetic dinoflagellate (Peridinium balticum); hindgut microbes in termites and woodroaches (Pyrsonympha, Barbulanympha and their associated spirochetes and other bacteria); sand dwelling and other ciliates and their associated bacteria; and so forth. The status of observations and artificial systems claiming evidence for transfer of genes between very distantly related organisms is critically discussed.A continuum from nearly completely autonomous partners (e.g., zoochlorellae in invertebrate animals) to nearly unrecognizable merged components (e.g., gamma particles in Blastocladiella) is found to exist among examples of extant organisms. The diversity and prevalence of such associations support the concept that there are many precedents for the steps hypothesized in the serial endosymbiotic theory of the origin of eukaryotic cells.     

Endophytic bacterial flora in the stem tissue of a tropical maize (<Emphasis Type="Italic">Zea mays</Emphasis> L.) genotype: isolation,identification and enumeration

The genotypic diversity of indigenous bacterial endophytes within stem of tropical maize (Zea mays L.) was determined in field and greenhouse experiments. Strains were isolated from stem tissues of a tropical maize cultivar (PEHM-1) by trituration and surface disinfestation and their population dynamics was determined. Endophytes were found in most of the growing season at populations ranging from 1.36–6.12 × 10⁵ colony-forming units per gram fresh weight (c.f.u./gm fw) of stem. Analysis of these bacterial endophytes using Gas Chromatography—Fatty Acid Methyl Ester (GC-FAME) led to the identification of Bacillus pumilus, B. subtilis, Pseudomonas aeruginosa and P. fluorescens as the relatively more predominant group of bacterial species residing in maize stem. When the maize seedlings grown in a greenhouse were inoculated with these four isolates individually, their population densities decreased (1.6–3.1 × 10⁵ c.f.u./gm fw of stem) as compared to the field-grown maize (1.8–3.8 × 10⁵ c.f.u./gm fw of stem). The highest persistence, however, was recovered in the case of B. subtilis with a population density of 3.1 × 10⁵ c.f.u./gm fw of stem tissue on 28 days after emergence (DAE). This is the first report on population dynamics of bacterial endophytes from tropical maize and the results establish that symptomless populations of bacteria exist in the maize stem.     

A Novel Electrochemically Active and Fe(III)-reducing Bacterium Phylogenetically Related to Clostridium butyricum Isolated from a Microbial Fuel Cell

An obligatory anaerobic bacterium was isolated from a mediator-less microbial fuel cell using starch processing wastewater as the fuel and designated as EG3. The isolate was Gram-positive, motile and rod (2.8–3.0 μm long, 0.5–0.6 μm wide). The partial 16S rRNA gene sequence and analysis of the cellular fatty acids profile suggested that EG3 clusters with Clostridium sub-phylum and exhibited the highest similarity (98%) with Clostridium butyricum. The temperature and pH optimum for growth were 37°C and 7.0, respectively. The major products of glucose and glucose/Fe(O)OH metabolism were lactate, formate, butyrate, acetate, CO₂and H₂. Growth was faster at the initial phase and the cell yield was higher when the medium was supplemented with Fe(O)OH than without Fe(O)OH. These results suggest that Fe(III) ion is utilised as an electron sink. Cyclic voltammetry showed that Clostridium butyricum EG3 cells were electrochemically active. It is a novel characteristic of strict anaerobic Gram-positive bacteria.     

Revealing Sulfate-Reducing Microorganisms in Oilfield Waters (Flysch Carpathians,South-eastern Poland)

Sulphidogenous microorganism communities were isolated from selected oilfield waters in the Flysch Carpathians of south-eastern Poland. Organisms were incubated using the microcosms method with application of two media: minimal medium and modified Postgate C medium with yeast extract or trisodium citrate or monocyclic hydrocarbons from the BTEX group (benzene, toluene, ethylbenzene, and xylene) as the sole carbon source. Activity of sulphidogenic, autochthonous microorganism communities was noted only on the Postgate medium. Beside active sulphate reduction – max. 70%, ca. 74% biodegradation of organic compounds was also observed in the cultures. The highest content of sulphate-reducing bacteria (SRB) in the COD (ca. 83%) was noted in cultures, in which trisodium citrate and yeast extract were applied as the sole carbon source. Molecular analysis indicated not only the presence of SRB such as Desulfobacterium autothrophicum, Desulfovibrio desulfuricans, but also other microorganisms, e.g., Geobacter metallireducens. All these taxa are obligatory or facultative anaerobes, with metabolism linked mostly with elemental sulphur and/or its oxidized forms, as well as iron. Analysis of the mineral composition of the residues confirmed the presence of elemental sulphur, testifying for the active reduction of sulphates by incompletely oxidizing sulphate reducers assigned to the SRB group. Based on the obtained results, it is concluded that the physical and chemical properties of the oilfield waters are favorable for the growth and development of sulphidogenic microorganism assemblages and mineral-forming processes conducted by them.     

Whole-cell biochips for bio-sensing: integration of live cells and inanimate surfaces

Recent advances in the convergence of the biological, chemical, physical, and engineering sciences have opened new avenues of research into the interfacing of diverse biological moieties with inanimate platforms. A main aspect of this field, the integration of live cells with micro-machined platforms for high throughput and bio-sensing applications, is the subject of the present review. These unique hybrid systems are configured in a manner that ensures positioning of the cells in designated patterns, and enables cellular viability maintenance, and monitoring of cellular functionality. Here we review both animate and inanimate surface properties and how they affect cellular attachment, describe relevant modifications of both types of surfaces, list technologies for platform engineering and for cell deposition in the desired configurations, and discuss the influence of various deposition and immobilization methods on the viability and performance of the immobilized cells.     

Aerobic submerged fermentation by acetic acid bacteria for vinegar production: Process and biotechnological aspects

Strictly aerobic acetic acid bacteria (AAB) have a long history of use in fermentation processes, and the conversion of ethanol to acetic acid for the production of vinegar is the most well-known application.At the industrial scale, vinegar is mainly produced by submerged fermentation, which refers to an aerobic process in which the ethanol in beverages such as spirits, wine or cider is oxidized to acetic acid by AAB. Submerged fermentation requires robust AAB strains that are able to oxidize ethanol under selective conditions to produce high-titer acetic acid. Currently submerged fermentation is conducted by unselected AAB cultures, which are derived from previous acetification stocks and maintained by repeated cultivation cycles.In this work, submerged fermentation for vinegar production is discussed with regard to advances in process optimization and parameters (oxygen availability, acetic acid content and temperature) that influence AAB activity. Furthermore, the potential impact arising from the use of selected AAB is described.Overcoming the acetification constraints is a main goal in order to facilitate innovation in submerged fermentation and to create new industry-challenging perspectives.     

Cyclic CMP and cyclic UMP mediate bacterial immunity against phages

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Biosynthesis of Cephalosporins

Abstract

Certain aerobic, Gram-negative bacteria, including the epiphytic plant pathogen, Pseudomonas syringae, possess a membrane protein that enables them to nucleate crystallization in supercooled water. Currently, these ice-nucleating (IN) bacteria are being used in snow making and have potential applications in the production and texturing of frozen foods, and as a replacement of silver iodide in cloud seeding. A negative aspect of these IN bacteria is frost damage to plant surfaces. Thus, of the various types of biological ice nucleators, bacteria have been the subject of most research and also appear relevant to the anticipated practical uses. The intent of this review is to explain the identification and ecology of the ice-nucleating bacteria, as well as to discuss aspects of molecular biology related to ice nucleation and consider existing and potential applications of this unique phenomenon.