Anaerobic biodegradation of pentachlorophenol by a methanogenic consortium

An anaerobic consortium degrading pentachlorophenol (PCP) by methanogenic fermentation was enriched from PCP-contaminated soils. In a semi-continuous reactor, PCP biodegradation was unstable and necessitated periodic additions of unacclimated anaerobic sludge waste to restore the activity. In continuous-flow reactors, PCP degradation activity was more stable when a mixture of glucose and sodium formate was used as secondary carbon source instead of glucose. The analysis of the chlorophenol intermediates suggested that the main pathway of PCP dechlorination was PCP 2,3,5,6-tetrachlorophenol 2,3,5-trichlorophenol 3,5-dichlorophenol 3-chlorophenol phenol. In a laboratory-scale continuous-upflow fixed-film column reactor, a PCP removal of more than 99% was achieved at a PCP loading rate of 60 mol (1 reactor volume)^–1 day^–1 for a hydraulic retention time of 0.7 day. Analysis of culture samples taken at different levels in the reactor have shown that, at this PCP loading rate, only the lower part of the reactor was active. 3-chlorophenol and 3,5- and 3,4-dichlorophenol were detected at the different levels of the reactor. A study of the microorganisms in the biofilm was carried out by scanning electron microscopy and suggested that the microorganisms involved in the consortium were present as a well-structured arrangement. Methanosaeta-like microorganisms were observed mainly at the base of the biofilm whereas, at the surface, a larger diversity of morphotypes was observed in which coccoid or small rod organisms were dominant. This work shows the importance of the design and the control of the operation parameters on the efficiency of the fixed-film reactor.     

Isolation and characterization of a new bacterium carboxylating phenol to benzoic acid under anaerobic conditions.

A consortium of spore-forming bacteria transforming phenol to benzoic acid under anaerobic conditions was treated with antibiotics to eliminate the four Clostridium strains which were shown to be unable to accomplish this reaction in pure culture and coculture. Clostridium ghonii was inhibited by chloramphenicol (10 micrograms/ml), whereas Clostridium hastiforme (strain 3) and Clostridium glycolicum were inhibited by clindamycin (20 micrograms/ml), without the transformation of phenol being affected. Electron microscopic observations of resulting liquid subcultures revealed the presence of two different bacilli: a dominant C hastiforme strain (strain 2) (width, 1 micron) and an unidentified strain 6 (width, 0.6 micron) which was not detected on solid medium. Bacitracin (0.5 U/ml) changed the ratio of the strains in favor of strain 6. C hastiforme 2 was eliminated from this culture by dilution. The isolated strain 6 transformed phenol to benzoic acid and 4-hydroxybenzoic acid to phenol and benzoic acid in the presence of proteose peptone. Both of these activities are inducible. This strain is a gram- variable, flagellated rod with a doubling time of 10 to 11 h in the presence of phenol. It has a cellular fatty acid composition like that of C. hastiforme. However, strain 6 does not hydrolyze gelatin or produce indole. The 16S rRNA sequence of strain 6 was found to be most similar to that of some Clostridium species, with homology ranging from 80 to 86%. Tbe evolutionary relationships of strain 6 to different groups of Clostridium and Clostridium-related species revealed that it does not emerge from any of these groups. Strain 6 most likely belongs to a new species closely related to Clostridium species.     

Interference of Neisseria gonorrhoeae growth by aerobic bacterial representatives of the urogenital flora

Aerobic bacterial isolates obtained from endocervical, vaginal and urethral swabbings were tested for interference of neisseria gonorrhoeae growth on solid medium. Simultaneous antagonism was studied using the lawn spotting method, and delayed antagonism by the basal spot/lawn method. From 58 swabbings we recuperated a total of 181 isolates, 71 of those were found interfering with at least one out of four gonococcal strains (G-1, G-2, G-3 and G-4). Similar percentages of interfering isolates were obtained from each of the isolation sites. The identification of the interfering isolates has revealed that similar numbers of coagulase negative staphylococci and identical numbers of group D streptococci were found for each of those sites. The majority of the interfering isolates and also of the inhibitory coagulase negative staphylococci showed only simultaneous antagonism. To complete the interference spectrum, we have tested all the active urogenital isolates against four other gonococcal strains (G-7, G-9, G-10 and G-11). This spectrum showed clearly that interference is not an all or none phenomenon. While the gonococcal interference spectrum of most of the Gram positive cocci and the Acinetobacter sp. strains is broad, that of all the other isolates is relatively narrow. Gonococcal strains G-7 and G-9 were the most susceptible to inhibition by the interfering urogenital isolates while strain G-3 was the most resistant one.     

Ice Nucleation Activity in Fusarium acuminatum and Fusarium avenaceum

Twenty fungal genera, including 14 Fusarium species, were examined for ice nucleation activity at −5.0°C, and this activity was found only in Fusarium acuminatum and Fusarium avenaceum. This characteristic is unique to these two species. Ice nucleation activity of F. avenaceum was compared with ice nucleation activity of a Pseudomonas sp. strain. Cumulative nucleus spectra are similar for both microorganisms, while the maximum temperatures of ice nucleation were −2.5°C for F. avenaceum and −1.0°C for the bacteria. Ice nucleation activity of F. avenaceum was stable at pH levels from 1 to 13 and tolerated temperature treatments up to 60°C, suggesting that these ice nuclei are more similar to lichen ice nuclei than to bacterial ones. Ice nuclei of F. avenaceum, unlike bacterial ice nuclei, pass through a 0.22-μm-pore-size filter. Fusarial nuclei share some characteristics with the so-called leaf-derived nuclei with which they might be identified: they are cell free and stable up to 60°C, and they are found in the same kinds of environment. Highly stable ice nuclei produced by fast-growing microorganisms have potential applications in biotechnology. This is the first report of ice nucleation activity in free-living fungi.     

Photoelectrochemical effects in the electrolyte-pigment-metal system

The electrolyte-pigment-metal system can be described as analogous to a photosensitive junction region. When the thickness of the pigment film is increased, the action spectra of the maximum short-circuit photocurrent under continuous illumination differ from the absorption spectra both in direct illumination (pigment-electrolyte) and in back illumination (metal-pigment). One is led to believe that there exist two photoactive regions in the system for the production of the short-circuit photocurrent; these two active regions are associated respectively with each interface. When the metallic semitransparent electrode is made of aluminum the two interfaces have opposite sign contributions to the photocurrent; this allows the determination of conditions in which one can observe specifically the contribution of the pigment-electrolyte interface, that is the interactions between excited pigment molecules and the redox system in the electrolyte.     

Determination of body surface area in neonatal swine.

The body surface area of 30 neonatal pigs of both sexes, weighing 445--1,976 g, were determined by the direct skinning technique. The range of measured body surface area values was 635--1,400 cm2 (mean = 895.1 cm2). The regression line, fitted to a scatter diagram and calculated by the least square method, was found to be Y = 337.2 + 0.553X; where X was body weight expressed in grams and Y was body surface area expressed in square centimeters.     

Foraging on patchily distributed prey by a cichlid fish (Teleostei,Cichlidae): A test of the ideal free distribution theory

Cichlid fish (Aequidens curviceps) distributed themselves and allocated their foraging time between two drift food patches in close approximation to the patch profitability ratio, as predicted by the ideal free distribution theory. The fish thereby achieved similar average feeding rates in the two patches, in two of three patch profitability ratio experiments. However, one major assumption of the ideal free model was violated, since individual fish differed in their competitive abilities for limited food resources, which resulted in unequal payoffs among individuals within each patch. Individual variation in feeding rates, and thus in competitive ability, was not related to despotism, but perhaps rather to individual differences in perceptual ability and in the ability to learn which patch was currently the more profitable. The strategy used by the fish to assess patch profitability included sampling available patches. However, individual fish switched (sampled) patches with varying frequency. Sampling had an associated cost, since high-frequency switchers had lower feeding rates on average than low-frequency switchers. Differences in foraging strategy among the fish therefore contributed to the observed in-equality in individual payoffs within patches.     

Do Males Form Social Associations Based on Sexual Attractiveness in a Fission-Fusion Fish Society?

Recent theory predicts that males should choose social environments that maximize their relative attractiveness to females by preferentially associating with less attractive rivals, so as to enhance their mating success. Using the Trinidadian guppy (Poecilia reticulata), a highly social species, we tested for non-random social associations among males in mixed-sex groups based on two phenotypic traits (body length and coloration) that predict relative sexual attractiveness to females and sexual (sperm) competitiveness. Based on a well-replicated laboratory dichotomous-choice test of social group preference, we could not reject the null hypothesis that focal males chose randomly between a mixed-sex group that comprised a female and a rival male that was less sexually attractive than themselves and another mixed-sex group containing a sexually more attractive male. The same conclusion was reached when females were absent from the two groups. As might be expected from these laboratory findings, free-ranging males in the field were not assorted by either body length or colour in mixed-sex shoals. The apparent lack of an evolved and expressed preference in wild male guppies from our study population to form social associations with other males based on their relative sexual attractiveness and competitiveness might be due to the fission-fusion dynamics of guppy shoals in nature. Such social dynamics likely places constraints on the formation of stable phenotype-based social associations among males. This possibility is supported by a simulation model which assumes group departure rules based on relative body size and coloration in males.