Methanobrevibacter smithii, a methanogen consistently colonising the newborn stomach.

Methanobrevibacter smithii is the main human methanogen almost always found in the digestive tract of adults. Yet, the age at which M. smithii establishes itself as part of the developing intestinal microflora remains unknown. In order to gain insight into this, we developed a polyphasic approach, including microscopic observation by fluorescence in situ hybridisation, polymerase chain reaction (PCR) sequencing detection, identification and culture, to isolate and genotype M. smithii in one-day-old newborns' gastric juice specimens. In the presence of negative controls, 50/50 (100%) prospectively analysed newborn gastric juice specimens were PCR-positive for methanogens, all identified as M. smithii by sequencing. We succeeded in cultivating M. smithii in 35/50 (70%) newborn gastric juice specimens, while 15/50 specimens remained sterile. Further, M. smithii was observed by direct microscopic investigation using fluorescence in situ hybridisation. Multispacer sequence typing found one of seven different genotypes per specimen, these genotypes having all been previously described in adult human stools. Methanobrevibacter smithii is an early inhabitant of the human stomach, colonising the gastric mucosa just after birth, and the mother's gut microbiota is a probable source of colonisation.

Release of organic matter in a discontinuously chlorinated drinking water network.

The effects of discontinuous chlorination on the characteristics of the water in a pilot drinking water distribution network were investigated. The release or consumption of organic matter (as dissolved organic carbon, DOC) following chlorination and non-chlorination periods were estimated, as were changes in bacterial cell production. In each unchlorinated network 0.3 mg DOCl(-1) was consumed and the average cell production was approximately 1.3 x 10(5) cells ml(-1). In discontinously chlorinated networks (chlorine treatment: 3.3 mg Cl2l(-1), chlorine residual: 0.1 mg Cl2l(-1)) the DOC release (DOCout-DOCin) was between 0.1 and 0.2 mg Cl(-1). Biomass production (cells(out)-cells(in)) during this chlorination period was lower (approximately 2 x 10(4) cells ml(-1)). The delay before DOC was released in chlorinated networks appeared to be less than 24 h, which corresponds to one hydraulic residence time. Likewise, when chlorination was stopped, 24 h or less were required before an efficient DOC removal was resumed. When chlorination was prolonged the observed release of DOC was progressively reduced from 0.2 mg l(-1) to zero, thus after 6 weeks of continuous chlorination the DOCin was equivalent to the DOCout.

Relationship between coliform culturability and organic matter in low nutritive waters.

The objective of this work was to investigate the behaviour of coliform bacteria in specific low nutritive waters conveying organic fractions from different origin of which an unknown part is likely to pass through the treatment barrier. For this purpose, we studied the growth (microscopic counting) and the culturability (count on nutritive medium) of ten coliform bacteria species as a function of the amount of organic matter in a river water collected after a period of heavy rain and in an algal bloom water. Assays were carried out in the presence of autochthonous heterotrophic bacteria from the Nancy (France) drinking water, with variable concentrations of dissolved organic carbon (DOC) representative of drinking waters (0.5-1.5 mg l(-1) for diluted river water samples and 1.3-2.5 mg l(-1) for diluted algal bloom water samples). Bacterial growth was measured in the two types of water, regardless of the initial concentration of DOC. We found that coliform bacteria lost their culturability in both sample series, and that the lower the initial DOC concentration the more rapidly the culturability was lost. The quantity of DOC consumed by the bacteria in the two water types (0.03-0.13 mg l(-1) in river water and 0.77-1.29 mg l(-1) in algal bloom water) and the resulting consequences on bacterial behaviour suggested that bloom water contains algal organic compounds that are antagonistic to the growth and/or the culturability of coliform bacteria. Organic matter thresholds, beyond which coliform bacteria are unlikely to keep their culturability, have not been determined experimentally. Indeed, at the end of the assays some culturable coliform bacteria were systematically detected in both types of water. Enterobacter cloacae was the predominant species. Thus, during these adverse events the probability of coliform occurrence can be considered as high in treated water.

Hydrolysis of wastewater colloidal organic matter by extracellular enzymes extracted from activated sludge flocs.

Enzymatic activities associated with the exopolymeric substances (EPSs) extracted from activated sludges were tested for their ability to hydrolyse the organic colloidal fraction of wastewater. Bacteria extracted with EPS and concentrated by wastewater microfiltration were inhibited with NaN3 or KCN. The protein hydrolysis mainly resulted from the enzymatic activity of EPS, whereas the glycolytic activity was mainly present in the organic colloidal fraction of the wastewater.

Factors influencing the biosorption of gadolinium by micro-organisms and its mobilisation from sand.

The present work was devoted to the study of the biosorption capacities of various microbial species (Bacillus subtilis, Pseudomonas aeruginosa, Ralstonia metallidurans CH34 previously Alcaligenes eutrophus CH34, Mycobacterium smegmatis, Saccharomyces cerevisiae) for ions of the lanthanide gadolinium (Gd3+). The uptake by sand of this element was also measured. Saturation curves and Scatchard models were established for all biosorbants used in this work. The results enabled us to determine the binding affinities and the maximum capacities for biosorption of Gd3+, which ranged from 350 micromol g(-1) for B. subtilis to 5.1 micromol g(-1) for S. cerevisiae. This study demonstrated the usefulness of optimisation of experimental conditions in biosorption investigations. Experimental results showed that biosorption could be influenced by the growth stage and by the composition of the growth medium of microbial cells. Finally, particular attention was given to the transfer of gadolinium ions from a loaded sand to a bacterial suspension.

The acute toxicity and in vivo antitumour activity against L1210 leukemia of triphenyltin 3,5-diisopropylsalicylate, bis (di-n-butyl-(s)-2-pyrrolidone-5-carboxylato)tin oxide and di-n-butyltin bis(3-amino-4-methylbenzoate).

Triphenyltin 3,5-di-isopropylsalicylate, compound 1, is characterized by a maximum tolerated dose (MTD) of 20 mg/kg. Bis[di-n-butyl(2-pyrrolidone-5-carboxylato)tin] oxide, compound 2, and (di-n-butyltin bis(3-amino-4-methyl-benzoate), compound 3, exhibit similar acute toxicities (MTD = 8 mg/kg) despite their lower in vitro activity, as compared to compound 1, against the two human tumor cell lines MCF-7 and WiDr. All three are inactive in vivo against L1210 leukemia in mice.