The Bradyrhizobium Sp. LmicA16 Type VI Secretion System Is Required for Efficient Nodulation of Lupinus Spp

Many bacteria of the genus Bradyrhizobium are capable of inducing nodules in legumes. In this work, the importance of a type VI secretion system (T6SS) in a symbiotic strain of the genus Bradyrhizobium is described. T6SS of Bradyrhizobium sp. LmicA16 (A16) is necessary for efficient nodulation with Lupinus micranthus and Lupinus angustifolius. A mutant in the gene vgrG, coding for a component of the T6SS nanostructure, induced less nodules and smaller plants than the wild-type (wt) strain and was less competitive when co-inoculated with the wt strain. A16 T6SS genes are organized in a 26-kb DNA region in two divergent gene clusters of nine genes each. One of these genes codes for a protein (Tsb1) of unknown function but containing a methyltransferase domain. A tsb1 mutant showed an intermediate symbiotic phenotype regarding vgrG mutant and higher mucoidity than the wt strain in free-living conditions. T6SS promoter fusions to the lacZ reporter indicate expression in nodules but not in free-living cells grown in different media and conditions. The analysis of nodule structure revealed that the level of nodule colonization was significantly reduced in the mutants with respect to the wt strain.

Degradation of Raw Starch by a Wild Amylolytic Strain of Lactobacillus plantarum

Lactobacillus plantarum A6, isolated from fermented cassava, can break down cassava raw starch that has not been subjected to preliminary physicochemical treatment. When the pH was kept at 6, the microorganism cultured in a bioreactor excreted a high alpha-amylase activity (60 U/ml). Synthesis of the enzyme occurred during the stationary phase and resulted in full hydrolysis of the cassava starch granules. This gave 41 g of lactic acid from 45 g of raw starch after 3 days of fermentation. Enzymatic attack was evident under scanning electron microscopy in the rougher appearance of the surface of starch granules and in the presence of large cavities in some of them. In contrast, when the pH was not regulated, only a small amount of alpha-amylase activity was produced (2 U/ml) and no decrease in the starch content of the medium was observed. However, under scanning electron microscopy, some granules displayed a rougher surface, which might have been the result of weak enzymatic attack.

Antimicrobial resistance survey in a river receiving effluents from freshwater fish farms

AIMS

The aims of this study were: (i) to determine the proportions of Aeromonas spp. resistant to florfenicol (FC), oxolinic acid (OA) and oxytetracycline (OTC) along a river receiving effluents from fish farms, and (ii) to assess the relevance of using this bacterial group as an indicator for studying the consequences of the use and release of these aquacultural antimicrobials in the freshwater environment, as compared with performing antimicrobial measurements in sediments.

METHODS AND RESULTS

Sediment interstitial waters sampled along a river during two distinct climatic seasons were plated on an Aeromonas-selective medium supplemented or not with OA, OTC or FC. The October 2004 campaign showed an enrichment of OA- and OTC-resistant Aeromonas immediately downstream of the fish farms and a wastewater treatment plant. Two fish farms showed similar results in March 2005. In contrast, only 10 FC-resistant Aeromonas strains could be isolated, which revealed that minimum inhibitory concentrations of FC were greater than 64 microg ml(-1) and multiple antimicrobial resistances. Contamination of sediments by antimicrobials was detected but was not always co-localized with resistance peaks or known point sources of contamination.

CONCLUSIONS

Aeromonas could be valuable indicators of OA, OTC and FC resistance in the freshwater environment. Fish farms contribute to the contamination of the river by antimicrobials and resistant bacteria.

SIGNIFICANCE AND IMPACT OF THE STUDY

Considering the still very low proportion of FC-resistant Aeromonas, this study can be considered as a reference for further studies about this recently introduced veterinary antimicrobial agent.

[ Nodulation of certain legumes of the genus Crotalaria by the new species Methylobacterium]

We studied a collection of 126 rhizobial isolates from eight species of Crotalaria (C. comosa, C. glaucoides, C. goreensis, C. hyssopifolia, C. lathyroides, C. perrottetii, C. podocarpa, and C. retusa) growing in Senegal. Nodulation and nitrogen-fixation tests on nine Crotalaria species revealed two specificity groups within the genus Crotalaria. Group I consists of plants solely nodulated by very specific fast-growing strains. Group II plants are nodulated by slow-growing strains similar to promiscuous Bradyrhizobium spp. strains already reported to nodulate many tropical legumes. SDS-PAGE studies showed that slow-growing strains grouped with Bradyrhizobium while fast-growing strains constituted a homogeneous group distinct from all known rhizobia. Amplified ribosomal DNA restriction analysis (ARDRA) of 10 representative strains of this group using four restriction enzymes showed a single pattern for each enzyme confirming the high homogeneity of group I. The 16S rDNA sequence analysis revealed that this specific group belonged to the genus Methylobacterium, thus constituting a new branch of nodulating bacteria.

Characterization of high-level fluoroquinolone resistance in Escherichia coli O78:K80 isolated from turkeys

Fluoroquinolone resistance was characterized in Escherichia coli O78:K80 isolated from diseased turkeys. The level of resistance to fluoroquinolones of the isolates appeared closely correlated with substitutions in GyrA and ParC, but not with the production of the AcrAB efflux pump. Among isolates highly resistant to ciprofloxacin (MIC 8 mg/L) and harbouring identical substitutions (two in GyrA and one in ParC), two close but distinguishable ribotypes were identified. This indicated that at least two independent selection events may have occurred.

Methylotrophic Methylobacterium bacteria nodulate and fix nitrogen in symbiosis with legumes

Rhizobia described so far belong to three distinct phylogenetic branches within the alpha-2 subclass of Proteobacteria. Here we report the discovery of a fourth rhizobial branch involving bacteria of the Methylobacterium genus. Rhizobia isolated from Crotalaria legumes were assigned to a new species, "Methylobacterium nodulans," within the Methylobacterium genus on the basis of 16S ribosomal DNA analyses. We demonstrated that these rhizobia facultatively grow on methanol, which is a characteristic of Methylobacterium spp. but a unique feature among rhizobia. Genes encoding two key enzymes of methylotrophy and nodulation, the mxaF gene, encoding the alpha subunit of the methanol dehydrogenase, and the nodA gene, encoding an acyltransferase involved in Nod factor biosynthesis, were sequenced for the type strain, ORS2060. Plant tests and nodA amplification assays showed that "M. nodulans" is the only nodulating Methylobacterium sp. identified so far. Phylogenetic sequence analysis showed that "M. nodulans" NodA is closely related to Bradyrhizobium NodA, suggesting that this gene was acquired by horizontal gene transfer.

Characterization of the common nodulation genes of the photosynthetic Bradyrhizobium sp. ORS285 reveals the presence of a new insertion sequence upstream of nodA

We isolated and characterized nodA genes from photosynthetic and non-photosynthetic rhizobia nodulating the legume genus Aeschynomene, and found that the nodA sequence from photosynthetic stem-nodulating bacteria was phylogenetically distant from the other already described nodA genes. Characterization of the photosynthetic strain ORS285 common nod gene cluster (nodABC) showed, upstream of nodA, the presence of a new insertion sequence element belonging to the IS3 family and specific to a group of photosynthetic strains from Aeschynomene.

Effect of Bradyrhizobium photosynthesis on stem nodulation of Aeschynomene sensitiva

Some leguminous species of the genus Aeschynomene are specifically stem-nodulated by photosynthetic bradyrhizobia. To study the effect of bacterial photosynthesis during symbiosis, we generated a photosynthesis-negative mutant of the Bradyrhizobium sp. strain ORS278 symbiont of Aeschynomene sensitiva. The presence of a functional photosynthetic unit in bacteroids and the high expression of the photosynthetic genes observed in stem nodules demonstrate that the bacteria are photosynthetically active during stem symbiosis. Stem inoculation by the photosynthetic mutant gave a 50% decrease in stem-nodule number, which reduced nitrogen fixation activity and plant growth in the same proportion. These results indicate an important role of bacterial photosynthesis in the efficiency of stem nodulation.

Photosynthetic bradyrhizobia are natural endophytes of the African wild rice Oryza breviligulata

We investigated the presence of endophytic rhizobia within the roots of the wetland wild rice Oryza breviligulata, which is the ancestor of the African cultivated rice Oryza glaberrima. This primitive rice species grows in the same wetland sites as Aeschynomene sensitiva, an aquatic stem-nodulated legume associated with photosynthetic strains of Bradyrhizobium. Twenty endophytic and aquatic isolates were obtained at three different sites in West Africa (Senegal and Guinea) from nodal roots of O. breviligulata and surrounding water by using A. sensitiva as a trap legume. Most endophytic and aquatic isolates were photosynthetic and belonged to the same phylogenetic Bradyrhizobium/Blastobacter subgroup as the typical photosynthetic Bradyrhizobium strains previously isolated from Aeschynomene stem nodules. Nitrogen-fixing activity, measured by acetylene reduction, was detected in rice plants inoculated with endophytic isolates. A 20% increase in the shoot growth and grain yield of O. breviligulata grown in a greenhouse was also observed upon inoculation with one endophytic strain and one Aeschynomene photosynthetic strain. The photosynthetic Bradyrhizobium sp. strain ORS278 extensively colonized the root surface, followed by intercellular, and rarely intracellular, bacterial invasion of the rice roots, which was determined with a lacZ-tagged mutant of ORS278. The discovery that photosynthetic Bradyrhizobium strains, which are usually known to induce nitrogen-fixing nodules on stems of the legume Aeschynomene, are also natural true endophytes of the primitive rice O. breviligulata could significantly enhance cultivated rice production.

Isolation and characterization of canthaxanthin biosynthesis genes from the photosynthetic bacterium Bradyrhizobium sp. strain ORS278

A carotenoid biosynthesis gene cluster involved in canthaxanthin production was isolated from the photosynthetic Bradyrhizobium sp. strain ORS278. This cluster includes five genes identified as crtE, crtY, crtI, crtB, and crtW that are organized in at least two operons. The functional assignment of each open reading frame was confirmed by complementation studies.

Multivariate data analysis using D-optimal designs, partial least squares, and response surface modeling: A directional approach for the analysis of farnesyltransferase inhibitors

We have investigated the combined use of partial least squares (PLS) and statistical design principles in principal property space (PP-space), derived from principal component analysis (PCA), to analyze farnesyltransferase inhibitors in order to identify "activity trends" (an approach we call a "directional" approach) and quantitative structure-activity relationships (QSAR) for a congeneric series of inhibitors: the benzo[f]perhydroisoindole (BPHI) series. Trends observed in the PCA showed that the descriptors used were relevant to describe our structural data set by clearly identifying two well-defined structural subclasses of inhibitors. D-Optimal design techniques allowed us to define a training set for PLS study in PP-space. Models were derived for each biological assay under evaluation: the in vitro Ki-Ras and cellular HCT116 tests. Each of these assay-based sets was subdivided once more into two subsets according to two structural classes in this BPHI series as revealed by the PCA model. The response surface modeling (RSM) methodology was used for each subset, and the corresponding RSM plots helped us identify "activity trends" exploited to guide further analogue design. For more precise activity predictions more refined PLS models on constrained PP-spaces were developed for each subset. This approach was validated with predicted sets and demonstrates that useful information can be extracted from just a few very informative and representative compounds. Finally, we also showed the potential use of such a strategy at an early stage of an optimization process to extract the first "activity trends" that might support decision making and guide medicinal chemists in the initial design of new analogues and/or lead followup libraries.

Evidence for active efflux as the primary mechanism of resistance to ciprofloxacin in Salmonella enterica serovar typhimurium

The occurrence of active efflux and cell wall modifications were studied in Salmonella enterica serovar Typhimurium mutants that were selected with enrofloxacin and whose phenotypes of resistance to fluoroquinolones could not be explained only by mutations in the genes coding for gyrase or topoisomerase IV. Mutant BN18/21 exhibited a decreased susceptibility to ciprofloxacin (MIC = 0.125 microg/ml) but did not have a mutation in the gyrA gene. Mutants BN18/41 and BN18/71 had the same substitution, Gly81Cys in GyrA, but exhibited different levels of resistance to ciprofloxacin (MICs = 2 and 8 microg/ml, respectively). None of the mutants had mutations in the parC gene. Evidence for active efflux was provided by a classical fluorimetric method, which revealed a three- to fourfold decrease in ciprofloxacin accumulation in the three mutants compared to that in the parent strain, which was annulled by addition of the efflux pump inhibitor carbonyl cyanide m-chlorophenylhydrazone. In mutant BN18/71, a second fluorimetric method also showed a 50% reduction in the level of accumulation of ethidium bromide, a known efflux pump substrate. Immunoblotting and enzyme-linked immunosorbent assay experiments with an anti-AcrA antibody revealed that the resistance phenotype was strongly correlated with the expression level of the AcrAB efflux pump and suggested that decreased susceptibility to ciprofloxacin due to active efflux probably related to overproduction of this pump could occur before that due to gyrA mutations. Alterations were also found in the outer membrane protein and lipopolysaccharide profiles of the mutants, and these alterations were possibly responsible for the decrease in the permeability of the outer membrane that was observed in the mutants and that could act synergistically with active efflux to decrease the level of ciprofloxacin accumulation.

Comparative studies of mutations in animal isolates and experimental in vitro- and in vivo-selected mutants of Salmonella spp. suggest a counterselection of highly fluoroquinolone-resistant strains in the field

The occurrence of mutations in the genes coding for gyrase (gyrA and gyrB) and topoisomerase IV (parE and parC) of Salmonella typhimurium experimental mutants selected in vitro and in vivo and of 138 nalidixic acid-resistant Salmonella field isolates was investigated. The sequencing of the quinolone resistance-determining region of these genes in highly fluoroquinolone-resistant mutants (MICs of 4 to 16 microg/ml) revealed the presence of gyrA mutations at codons corresponding to Gly-81 or Ser-83, some of which were associated with a mutation at Asp-87. No mutations were found in the gyrB, parC, and parE genes. An assay combining allele-specific PCR and restriction fragment length polymorphism was developed to rapidly screen mutations at codons 81, 83, and 87 of gyrA. The MICs of ciprofloxacin for the field isolates reached only 2 microg/ml, versus 16 microg/ml for some in vitro-selected mutants. The field isolates, like the mutants selected in vivo, had only a single gyrA mutation at codon 83 or 87. Single gyrA mutations were also found in highly resistant in vitro-selected mutants (MIC of ciprofloxacin, 8 microg/ml), which indicates that mechanisms other than the unique modification of the intracellular targets could participate in fluoroquinolone resistance in Salmonella spp. A comparison of experimental mutants selected in vitro, field strains, and mutants selected in vivo suggests that highly fluoroquinolone-resistant strains are counterselected in field conditions in the absence of selective pressure.

Photosynthetic bradyrhizobia from Aeschynomene spp. are specific to stem-nodulated species and form a separate 16S ribosomal DNA restriction fragment length polymorphism group

We obtained nine bacterial isolates from root or collar nodules of the non-stem-nodulated Aeschynomene species A. elaphroxylon, A. uniflora, or A. schimperi and 69 root or stem nodule isolates from the stem-nodulated Aeschynomene species A. afraspera, A. ciliata, A. indica, A. nilotica, A. sensitiva, and A. tambacoundensis from various places in Senegal. These isolates, together with 45 previous isolates from various Aeschynomene species, were studied for host-specific nodulation within the genus Aeschynomene, also revisiting cross-inoculation groups described previously by D. Alazard (Appl. Environ. Microbiol. 50:732-734, 1985). The whole collection of Aeschynomene nodule isolates was screened for synthesis of photosynthetic pigments by spectrometry, high-pressure liquid chromatography, and thin-layer chromatography analyses. The presence of puf genes in photosynthetic Aeschynomene isolates was evidenced both by Southern hybridization with a Rhodobacter capsulatus photosynthetic gene probe and by DNA amplification with primers defined from photosynthetic genes. In addition, amplified 16S ribosomal DNA restriction analysis was performed on 45 Aeschynomene isolates, including strain BTAi1, and 19 reference strains from Bradyrhizobium japonicum, Bradyrhizobium elkanii, and other Bradyrhizobium sp. strains of uncertain taxonomic positions. The 16S rRNA gene sequence of the photosynthetic strain ORS278 (LMG 12187) was determined and compared to sequences from databases. Our main conclusion is that photosynthetic Aeschynomene nodule isolates share the ability to nodulate particular stem-nodulated species and form a separate subbranch on the Bradyrhizobium rRNA lineage, distinct from B. japonicum and B. elkanii.

Molecular characterization of the alpha-amylase genes of Lactobacillus plantarum A6 and Lactobacillus amylovorus reveals an unusual 3' end structure with direct tandem repeats and suggests a common evolutionary origin

The alpha-amylase gene (amyA) of Lactobacillus plantarum A6 was isolated from the genome by polymerase chain reaction with degenerated oligonucleotides, synthesized according to the tryptic peptide amino acid sequences of the purified enzyme. Nucleic acid sequence analysis revealed one open reading frame of 2739 bp encoding a 913 amino acid protein. The amylase appears to be divided into two equal parts. The N-terminal part has the typical characteristics of the well-known alpha-amylase family (65% identity with the alpha-amylase of Bacillus subtilis and 97% identity with the partial sequence available for the alpha-amylase of Lactobacillus amylovorus). The C-terminal part displays a fairly unusual structure. It consists of four direct tandem repeated sequences of 104 amino acids sharing 100% similarity. The complete nucleotide sequence of the alpha-amylase gene of L. amylovorus was also determined. An open reading frame of 2862 bp encoding a 954 amino acid protein was identified. Perfect homology between the two amyA genes was observed in the N-terminal region. The C-terminal part of L. amylovorus alpha-amylase also included tandem repeat units but striking differences were observed: (i) the addition of one repeat unit; (ii) a shorter, 91 amino acid repetition unit. These structural homologies suggest that both genes have a common ancestor and may have evolved independently by duplication with subsequent recombination and mutation.

Age and gender-related incidence of chronic renal failure in a French urban area: a prospective epidemiologic study

OBJECTIVE

To determine the age- and gender-related incidence of chronic renal failure in a French urban area.

METHODS

Prospective study of adult patients newly identified as having established, chronic renal failure defined by serum creatinine (Scr) > or = 200 mumol/l, with the cooperation of all nephrology and dialysis units in the Ile de France district (10,660,000 inhabitants) during a 1-year period.

RESULTS

2775 patients (1780 males, 995 females) were referred with Scr > or = 200 mumol/l between July 1991 and June 1992, an overall incidence of 260/million population. 847 had advanced renal failure (Scr > or = 500 mumol/l) and 541 patients (19.5%) were > or = 75 years of age. The age-related incidence was 92, 264, 523 and 619/million population in the age groups 20-39, 40-59, 60-74 and > or = 75 years old, respectively. The annual incidence was twice as high in males than in females up to 75 years and three times as high in patients > or = 75 years (1124 vs 356/million population). Based on the proportion of patients reaching end-stage renal failure within one year of referral, the minimal estimation of the need for supportive therapy is 81/million/year.

CONCLUSIONS

This epidemiological study in a large French urban area indicates an incidence of 260 patients per million population annually referred to nephrology units for chronic renal failure defined by Scr > or = 200 mumol/l, with a marked preponderance of males and a dramatic increase of incidence with age in both genders.

[Demography and effects of chronic renal insufficiency in Ile-de-France]

In order to assess the incidence of chronic renal failure (CRF) and the demographic characteristics of affected patients, a prospective, multicenter epidemiologic study was conducted with the cooperation of all nephrology and dialysis units in the Ile-de-France district, the total population of which is 10660000 inhabitants (source: national census, march 1990). Included were patients with a plasma creatinine (Pcr) concentration > or = 200 mumol/l referred during the one-year period from July 1, 1991 until June 30, 1992. The overall response rate was 98.5%. A total of 2775 adult patients were recorded, including 1780 males (64%) with a mean (+/- SD) age of 58.1 +/- 16.3 years and a mean Pcr of 447 +/- 214 mumol/l, and 995 females (36%) with a mean age of 59.2 +/- 16.4 years and a mean Pcr of 425 +/- 185 mumol/l. Age of patients was < 40 in 16%, 40-59 in 31%, 60-74 in 34% and > or = 75 years in 19%. Pcr was 200-399 mumol/l in 54%, 400-599 mumol/l in 25%, 600-799 mumol/l in 12% and > or = 800 mumol/l in 9%. The overall incidence of CRF was 260/million population/year, twice higher in males than in females (348 vs 179/10(6)/year, p < 0.001). Incidence of CRF dramatically rose with age in both genders, with figures as high as 1124 and 356/10(6)/year respectively in male and female patients aged > or = 75 years, vs 288 and 151/10(6)/year in patients aged < 40 years. A sequential evaluation was performed in a representative sample of 251 patients with initial Pcr > or = 300 mumol/l. End-stage renal failure (ESRF) was reached within one year in 99% of patients with PCr > 600, 49% with Pcr 500-599, 24% with PCr 400-499 and 11% with PCr 300-399 mumol/l. Based on these figures, the predicted incidence of ESRF within one year of referral was 864 out of the 2775 patients, an estimated annual incidence of 81 patients per million population. In conclusion, this prospective study affords the first direct information on the incidence of chronic renal failure and the demographic characteristics of patients with CRF in the Ile-de-France district. Due to the design of the study conducted only in nephrology units, the estimated figure of 81 new patients per million population per year reaching ESRF is a minimal evaluation. In view of the relentless aging of population in France, an incidence of at least 100 ESRF patients per million population per year is to be expected in the next future.

[Voluntary barium poisoning]

A 45-year-old man attempted to commit suicide by ingesting a large amount of barium. In some hours, he experienced generalized muscle weakness with hypokalaemia, treated by large dose of potassium (440 mmol in the first day). This weakness resulted in difficulties in swallowing and respiratory failure requiring mechanical ventilation. An anuric renal insufficiency started early, requiring haemodialysis for three weeks. It was induced probably by renal toxicity of barium and recovered completely. Later, the patient experienced an extrapyramidal syndrome initiated by tremor and myoclonia. Hypertonia induced a parkinsonian rheumatism, fixing the two hands in an irreducible position. There was also a contracture of superior sphincter of oesophagus, with severe disturbance of deglutition, ending after three months only. MRI study showed a bilateral hypersignal in basal ganglia and thalamus. It remains unknown whether this neurological syndrome was toxic or ischaemic. This patient remained under mechanical ventilation for three months because of disturbances of deglutition. He was discharged to his home at the 6th month. One year later he was still adynamic, but able to carry our rather precise movements.

[In vitro effect of cefixime against 200 strains of Branhamella catarrhalis. Comparison with cefotaxime]

The in vitro activity of cefixime was tested against 200 strains of Branhamella catarrhalis. Of these strains, 146 had been collected during 1987 from 15 different "Centres hospitaliers généraux", through a multicenter collaborative investigation organized by the "Collège de Bactériologie-Virologie-Hygiène des hôpitaux généraux". The remaining 54 strains were isolated at the "Centre hospitalier", of Aix-en-Provence. The strains originated from: bronchopulmonary collections: 80.2 per cent, sinusitis: 5.6 per cent, conjunctivitis: 4.6 per cent, otitis: 3.5 per cent, blood cultures: 0.5 per cent, miscellaneous: 5.6 per cent. Seventy-three per cent of the strains produced beta-lactamases. MIC determination was performed according to the agar dilution procedure on non-enriched Mueller-Hinton agar (30 hours incubation at 37 degrees C without CO2). The inoculum was 10(5) CFU per spot. Non beta-lactamase producing strains displayed the following MIC 50 and MIC 90 values (mg/l): amoxicillin: 0.03 - 0.125; cefotaxime: 0.06 - 1; cefixime: 0.06 - 0.5. Beta-lactamase producing strains were generally more resistant: amoxicillin: 32 - 128; cefotaxime: 1 - 2, and cefixime: 0.5 - 1.

Expression of Tn5-encoded streptomycin resistance in E. coli

Four Tn5 mutations able to express streptomycin resistance in E. coli were obtained independently. These mutations (called Tn5) were localized and sequenced. All of them consist of a 6 bp deletion in the str gene near the 3' end. The mutation affects a region peculiar for its repetition of an identical 6 bp sequence. The mutation does not affect the level of transcription of the kan, ble, str operon of Tn5, neither does it increase the level of translation of str. The mutation seems to interfere with a post-translational event.

Completion of the nucleotide sequence of the central region of Tn5 confirms the presence of three resistance genes

The DNA sequence of the region located downstream from the kanamycin resistance gene of Tn5 up to the right inverted repeat IS50R has been determined. This completes the determination of the sequence of Tn5 which is 5818 bp long. The 2.7 Kb central region contains three resistance genes: the kanamycin-neomycin resistance gene, a gene coding for resistance to CL990 an antimitotic-antibiotic compound of the bleomycin family and a third gene that confers streptomycin resistance in some bacterial species but is cryptic in E. coli. A Tn5* mutant able to express streptomycin resistance in E. coli was isolated. With this mutant, it was demonstrated that in E. coli the expression of the three resistance genes is coordinated in a single operon.

[Thoracic opacity in a newborn infant disclosing an adenomatoid cyst of the lung. Radio-echographic case]

In a preterm infant (28 week gestation), the chest film performed at 1 hour of life because of mild respiratory insufficiency showed a massive opacity of the right hemithorax. Congenital cystic adenomatoid malformation was suspected on the basis of ultrasonographic findings of multiple cysts. It was confirmed by further X ray examination and pathologic findings. This unusual case shows the ultrasonographic pattern and X ray evolution of this rare malformation.