Physiological Status and Community Composition of Microbial Mats of the Ebro Delta, Spain, by Signature Lipid Biomarkers.

Physiological status of microbial mats of the Ebro Delta (Tarragona, Spain) based on the extraction of lipids considered "signature lipid biomarkers" (SLB) from the cell membranes and walls of microorganisms has been analyzed. Data from a day-night cycle show significant differences in viable cells countings (PLFA cells counts) ranging from 1.5 x 10(10) to 5.0 x 10(10) cells g(-1) of sediment. Minimum values were observed at 18:00 and 6:00, when physicochemical conditions change drastically. The diversity of the microbial community was assessed by GC/MS analysis of phospholipid fatty acids (PLFA). The ratio of PLFA, representative of Gram-negative bacteria, comprises 47.8% of the total PLFA of the microbial mat community. The remaining PLFA was representative of Gram-positive (10.0%), anaerobic (5.7%), and eukaryotic microorganisms (5.7%), and other common lipids. Two different approaches were used as a comparative study to assess the physiological status of the microbial mats. Two parameters (cyclopropane fatty acids/omega7c monoenoic fatty acids, and measurement of the trans/cis monoenoic PLFA ratio) showed a minimum at midnight, suggesting the highest microbial activity. Higher values were observed at 18:00 and 6:00, coinciding with lower PLFA cell counts.

[4 years of Microbiología SEM (1994-1997)]. / Cuatro años de Microbiología SEM (1994-1997).

Different aspects of Microbiología SEM editorial process over the years 1994-1997 are analyzed: number of originals received, the process leading to their publication, rates of accepted and refused papers, time needed for each step of the editorial process--which comprises scientific, language editing, if needed--, as well as some characteristics that can define the patterns of the articles, such as number of authors, institutions where the authors work and mean number of references. The contents of the different sections (editorial, research and review articles, perspectives, opinion, books review) are commented on, as well as the role played by some of them as forums for the discussion of topics of current scientific interest, especially the editorials focusing on the state-of-the-art of microbiological research in Latin American countries. Characteristics and frequency of monographic issues are also presented. The information is complemented with data about the circulation and distribution of the journal, its inclusion in international indexes and its current electronic publication on the world wide web.

High degree of similarity between Chromatium vinosum and Chromatium minutissimum as revealed by riboprinting.

The riboprinting technique (restriction fragment length polymorphism [RFLP] analysis of PCR-amplified ribosomal DNA) was used to study five strains representing three species of the genus Chromatium. An RFLP analysis following digestion of the amplified small-subunit ribosomal DNA with 25 restriction enzymes revealed that the patterns obtained for all strains of Chromatium vinosum were identical. Chromatium gracile was different from C. vinosum with seven enzymes. On the other hand, Chromatium minutissimum produced the same patterns as C. vinosum with all enzymes, indicating that these organisms have a high degree of similarity. An RFLP analysis of the PCR-amplified spacer sequence between the 16S and 23S ribosomal DNAs gave similar results except that there was a larger number of differences between C. gracile and the other organisms examined.

Biodegradation of Poly-(beta)-Hydroxyalkanoates in a Lake Sediment Sample Increases Bacterial Sulfate Reduction.

The addition of a poly-(beta)-hydroxyalkanoate (PHA) to incubation bottles containing anaerobic sediment from Lake Ciso (Banyoles, Catalonia, northeast Spain) was correlated with an increase in sulfide production. The concentration of PHA diminished to 51 to 99% of the initial amount. Sodium molybdate (1 mM) decreased the rate of PHA degradation and inhibited sulfide production, thus indicating that PHAs serve as carbon and electron sources for sulfate reduction.

Microbial degradation of poly-beta-hydroxyalkanoates.

The search for new materials that are not hazardous to the environment has become a major issue in our society, engaged as it is in the attainment of sustainable development. Poly-beta-hydroxyalkanoates (PHA), produced exclusively by prokaryotes, can be used as thermoplastics and are fully biodegradable and innocuous to the environment. Biodegradability testing has quantified the capacity of microorganisms to degrade such new chemical compounds, particularly polyhydroxyalkanoates. Standardized tests may also discover new microorganisms and environmental conditions that accelerate biodegradation. We evaluate various techniques used to assess the biodegradability of PHA, and which may also be applied to test other kinds of polymers.