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The new european régulation spécifies that drinking water quality should now be assessed at the consumer's tap rather than at the outlet of treatment plants. So, it is very important for all drinking water producers and suppliers, whatever their analytical means are, to have efficient tools for the quantification of biofilms, so that they can detect problems and react as quickly as possible. Thus, on the basis of a previous european programme research, we developed and tested a simple and easily reproducible experimental procedure to assess the biofilm formation potential of waters.Sturdy stainless steel incubators, highly adapted to industrial field conditions and containing glass beads were designed to allow the biofilm formation and the measurement of technically basic parameters (HPC) or more complex parameters (Fixed Total Organic Carbon, fixed total bacteria).Such incubators were connected to a surface water after a slow sand filtration stage. The maximal quantities measured were lower than those typically reported in the literature: about 103/cm2for HPC-R2A, 104/cm2for total bacteria and 0.5 µg/cm2for Fixed Total Organic Carbon (FTOC).A significant linear relationship exists between FTOC and total bacteria or HPC but it seems that the most part of FTOC is of extra-cellular origin.More generally, the resutts obtained validate the use of this type of incubators as a monitoring System which is a suitable tool for all potable water producers and suppliers.

Gene replacement and integration in a Corynebacterium glutamicum ATCC 21086 derivative were achieved by transformation with a nonreplicative plasmid that contains the C. glutamicum ATCC 17965 gdhA gene modified by the insertion of an aphIII cartridge. We isolated rare derivatives of the integrative transformants that have higher levels of expression of the integrated plasmid genes than the parent. Different types of such amplified clones were distinguished according to their antibiotic resistance levels, enzyme specific activities, and physical structures. All amplified clones share a structural DNA motif confined to the chromosomal gdhA locus: a variable number (up to 10) of tandem copies of a unit that includes the selected gene and one flanking repeat. A given clone contains subpopulations that differ in the number of repeats of this unit.

SummaryOne hundred and eight single or multi-point crosses involving frameshift mutants in the A group of intragenic suppression were analysed. The frequencies of coconversion were always very high ( > 0·94). Two parameters were considered: the frequency of conversion and the disparity values of conversion (i.e. the ratio of 6 + : 2m to 2 + : 6m asci). The pattern of variation of the disparity values agrees with an equal influence of the associated heterozygous sites in determining the direction of conversion.This suggests that the excision process needed for heteroduplex correction proceeds in both directions from the one stranded nick provoked by the mismatch, i.e. that there is no important excision polarity. It also suggests that recognition of the mismatch prior to nicking is not part of a polar process.The positive correlation observed between the disparity value and the frequency of conversion is considered as new evidence for frequent symmetrical distribution of hybrid DNA in the region studied.Heredity (1979) 42, 337–352; doi:10.1038/hdy.1979.37

Two recessive mutants spo76 and spo77, altered in U.V. sensitivity, protoplast regeneration and meiotic recombination were isolated in Sordaria macrospora. The suppression of the spo76 phenotype by spo77 suggests that they are involved in the same pathway. The asynaptic spo77 exhibits a rare synaptonemal complex (SC) with abnormally thick and double lateral elements (LE). In spo76, an early centromere cleavage leads to a meiotic arrest after metaphase I; SC are formed, but their discontinuous LE appear to be either unique or split into two thin LE. It is suggested that the corresponding wild-type functions are required for the sister chromatid cohesiveness.

Reconstruction of serially sectioned zygotene and pachytene nuclei has allowed, by measuring the lengths of synaptonemal complexes, an assignment of the 7 linkage (LG) groups to the 7 chromosomes in the fungus Sordaria macrospora. The 7 LG have been established using 19 mutants showing low second division segregation frequencies. Eight chromosomal rearrangements mapped on the 7 LG were used to identify the chromosomes involved. The following one to one assignment of the 7 LG to specific chromosomes was obtained: LG a: chromosome (chr) 1, LG b: chr5, LG c: chr6, LG d: chr7, LG e: chr4, LG f: chr3 and LG g: chr2 (the chromosome carrying the nucleolus organizer region).

Two two-point crosses in coupling alignement were made between intragenic suppressors at the locus b2. The phenotype of the double mutant is distinguishable both from that of the wild type and of the single mutant. Thus one can select all kinds of recombination events.

Sixty two ascospore colour mutants have been induced in Ascobolus immersus: 25 by an acridine (ICR170), 18 by N-methyl-N'-nitro-N-nitrosoguanidine (NG) and 19 by ethyl methanesulfonate (EMS). All these mutants have been crossed to the wild type strain and their conversion spectrum has been determined. It appears that the conversion spectrum is closely related to the origin of the mutants studied with respect to the mutagen by which they were induced. All NG mutants gave numerous asci with postmeiotic segregation and an excess of conversion to wild type over conversion to the mutant type. ICR mutants gave no postmeiotic segregation and an excess of conversion to the mutant type. The majority of EMS mutants behave like NG mutants, but some showed only meiotic segregation with either an excess of conversion to the mutant type or an excess of conversion to wild type. These data are in good agreement with the hypothesis that the nature of the mutation has a strong influence on the conversion spectrum.

In order to establish a relationship between the type of genetic alteration occurring in the mutant and the conversion spectrum which is associated with it, an attempt was made to characterize the genetic alterations in a sample of five spore colour mutants by specific reversion.

Plasmid DNA was efficiently electro-transformed into intact cells of nine Corynebacteria strains belonging to Brevibacterium lactofermentum, Brevibacterium flavum, Corynebacterium glutamicium and Corynebacterium melassecola. Relationships were explored between transformation efficiency and parameters such as electric field strength and pulse length, DNa concentration, physiological state and concentration of the cells. In optimal conditions, more than 107 transformants per μg of DNa could be obtained. Electrotransformation with plasmid DNA isolated from different sources indicates that DNA modification may play a role in transformation efficiency.