Characterization of type II protein secretion (xcp) genes in the plant growth-stimulatingPseudomonas putida, strain WCS358

InPseudomonas aeruginosa, the products of thexcp genes are required for the secretion of exoproteins across the outer membrane. Despite structural conservation of the Xcp components, secretion of exoproteins via the Xcp pathway is generally not found in heterologous organisms. To study the specificity of this protein secretion pathway, thexcp genes of another fluorescent pseudomonad, the plant growth-promotingPseudomonas putida strain WCS358, were cloned and characterized. Nucleotide sequence analysis revealed the presence of at least five genes, i.e.,xcpP, Q, R, S, andT, with homology toxcp genes ofP. aeruginosa. Unlike the genetic organization inP. aeruginosa, where thexcp cluster consists of two divergently transcribed operons, thexcp genes inP. putida are all oriented in the same direction, and probably comprise a single operon. Upstream ofxcpP inP. putida, an additional open reading frame, with no homolog inP. aeruginosa, was identified, which possibly encodes a lipoprotein. Mutational inactivation ofxcp genes inP. putida did not affect secretion, indicating that no proteins are secreted via the Xcp system under the growth conditions tested, and that an alternative secretion system is operative. To obtain some insight into the secretory pathway involved, the amino acid sequence of the N-terminus of the major extracellular protein was determined. The protein could be identified as flagellin. Mutations in thexcpQ andR genes ofP. aeruginosa could not be complemented by introduction of the correspondingxcp genes ofP. putida. However, expression of a hybrid XcpR protein, composed of the N-terminal one-third ofP. aeruginosa XcpR and the C-terminal two-thirds ofP. putida XcpR, did restore protein secretion in aP. aeruginosa xcpR mutant.     

Carotenoids protectPhaffia rhodozyma against singlet oxygen damage

Summary The only known habitat of the astaxanthin-containingPhaffia rhodozyma is in slime fluxes of deciduous trees at high altitudes. In this habitat, the function of carotenoids inP. rhodozyma is probably to provide protection against photogenerated antifungal substances in the tree flux such as singlet oxygen (¹O₂). To investigate the role of carotenoids inP. rhodozyma, genetic selections were employed to determine if carotenogenic yeast strains ofP. rhodozyma have enhanced ability to quench¹O₂. Singlet oxygen was generated in liquid culture by the interaction of visible light (-550 nm) with the photosensitizer rose bengal or by the activation of -terthienyl with ultraviolet light (=366 nm). In each case the treatments selected for growth of pigmented strains ofP. rhodozyma. Albino (carotenoid-less) or yellow (-carotene producing) strains grew less well in media containing¹O₂. Addition of the¹O₂ quencher sodium azide to the medium with -terthienyl allowed growth of non-pigmented strains. Since the ecological niche ofP. rhodozyma is highly specific, we investigated whether extracts of birch trees (Betula), the original source ofP. rhodozyma, contained a compound that would select for pigmented populations of the yeast. WhenP. rhodozyma strains were exposed to ethyl acetate extracts ofBetula papyrifera excited with 366 nm ultraviolet light, only pigmented cells were able to grow. These results suggest that carotenogenesis developed inP. rhodozyma in response to the presence of photoactivatable antifungal compounds produced by the host tree.This paper is dedicated to Professor Herman Jan Phaff in honor of his 50 years of active research which still continues.     

rbcL sequences support exclusion ofRetzia,Desfontainia, andNicodemia from theGentianales

The taxonomic positions ofRetzia, Desfontainia, andNicodemia have been much discussed, and all three genera have been included inLoganiaceae (Gentianales). We have made a cladistic analysis ofrbcL gene sequences to determine the relationships of these taxa toGentianales. Four newrbcL sequences are presented; i.e., ofRetzia, Desfontainia, Diervilla (Caprifoliaceae), andEuthystachys (Stilbaceae). Our results show thatRetzia, Desfontainia, andNicodemia are not closely related toLoganiaceae or theGentianales. Retzia is most closely related toEuthystachys and is better included inStilbaceae. The positions ofDesfontainia andNicodemia are not settled, butDesfontainia shows affinity for theDipsacales s.l. andNicodemia for theLamiales s.l.     

Enhancement ofcis,cis-muconate productivity by overexpression of catechol 1,2-dioxygenase inPseudomonas putida BCM114

For enhancement ofcis,cis-muconate productivity from benzoate, catechol 1,2-dioxygenase (C12O) which catalyzes the rate-limiting step (catechol conversion tocis,cis-muconate) was cloned and expressed in recombinantPseudomonas putida BCM114. At higher benzoate concentrations (more than 15 mM),cis,cis-muconate productivity gradually decreased and unconverted catechol was accumulated up to 10 mM in the case of wildtypeP. putida BM014, whereascis,cis-muconate productivity continuously increased and catechol was completely transformed tocis,cis-muconate forP. putida BCM114. Specific C12O activity ofP. putida BCM114 was about three times higher than that ofP. putida BM014, and productivity was enhanced more than two times.     

Expression ofKlebsiella pneumoniae nif genes inProteus mirabilis

Self-transmissible plasmids carryinghis andnif genes fromKlebsiella pneumoniae have been introduced into threehis mutants ofProteus mirabilis: strains 5006-1, WR19 and WR20. Expression ofhis by the transconjugants was unequivocal, if slightly temperature-sensitive, but none was Nif⁺ when tested for acetylene reduction in anaerobic glucose medium using inocula from rich or glucose-minimal aerobic agar cultures. Succinate or pyruvate in place of glucose, low glucose, lower temperature or elevated Na₂MoO₄ did not allownif expression and no nitrogenase MoFe-protein peptide was detected immunologically after exposure to conditions in which diazotrophic enterobacteria, normal or genetically constructed, derepressnif.One strain,P. mirabilis WR19, carrying thehis nif Km^r plasmid pMF250 was examined in detail. Thenif activator genenifA was introduced on the plasmid pCK1. Such derivatives remained Nif^- when tested, after aerobic growth on rich agar media, with normal or low glucose, with succinate or with elevated Mo. However, pre-conditioning by aerobic growth on glucose-minimal agar led to subsequent anaerobic expression ofnif in glucose medium from pMF250 in WR19 carrying pCK1. NH ₄ ⁺ or proline could serve as N-source in the glucose-minimal agar. Maximum activity was about 5% of that ofK. pneumoniae in our assay conditions. Material cross-reacting with anti-serum to the nitrogenase MoFe protein was formed. Nitrogenase activity was not switched off by NH ₄ ⁺ .P. mirabilis WR19 (pCK1) showed NH ₄ ⁺ -constitutive temperature-sensitive kanamycin resistance (anif-related phenotype of this plasmid) in aerobic glucose minimal medium. Expression ofnif inP. mirabilis WR19 (pCK1, pMF250) was NH ₄ ⁺ -repressible despite the constitutivenifA character of pCK1 and introduction of thentrA ⁺ plasmid pMM17 did not alter this phenotype. However, pCK1 did not give rise to NH ₄ ⁺ -constitutive diazotrophy in the wild-typeK. pneumoniae M5al. A construct of WR19 carrying pMF250 and constitutiventrC plasmid (pMD45) remained Nif^- even after pre-growth on glucose-minimal media.We conclude (a) thatP. mirabilis forms a gene product functionally equivalent to that ofntrA inK. pneumoniae, (b) that it forms no functional equivalent of thentrC product in our growth conditions. The need for pre-conditioning on aerobic glucose media remains perplexing.Non-common abbreviation NFDM Nitrogen-free-Davis-Mingioli medium     

Analysis of genome-specific sequences inPhleum species: Identification and use for study of genomic relationships

Sau3AI shot gun cloning and colony hybridization with total genomic probes were used to isolate genome-specific sequences inPhleum species. The total DNA isolated from diploid speciesP. alpinum andP. bertolonii was partially digested withSau3AI and cloned using pUC19 as a vector to anE. coli strain DH5mcr. A partial genomic DNA library consisting of 3030 colonies for the genome ofP. alpinum and one consisting of 3240 colonies for the genome ofP. bertolonii were constructed. Twelve hundred and thirty colonies from the DNA library ofP. alpinum and 1320 from that ofP. bertolonii were respectively blotted to membrane filters and hybridized to the total genomic probes from these two species. Eight clones specific toP. alpinum and 13 specific toP. bertolonii were isolated through colony hybridization and further dot-blot hybridization. Most of these clones may carry highly or moderately repetitive sequences. Three sequences specific toP. alpinum and 3 specific toP. bertolonii were used as probes to hybridize theEcoRI-digested DNA samples from four species,P. alpinum,P. bertolonii,P. pratense andP. montanum, on Southern blot. The results from these hybridization experiments showed that all 3P. bertolonii-specific probes and 2 of the 3P. alpinum-specific probes hybridized to the DNA ofP. pratense, thus confirming the conclusion of the close relationships between the cultivated timothy and its two wild relatives that was drawn in our previous study using the C-banding technique.     

Analyses of<Emphasis Type="Italic"> cis</Emphasis> -acting elements that affect the transposition of<Emphasis Type="Italic"> Mos1 mariner</Emphasis> transposons in vivo

The left (5) inverted terminal repeat (ITR) of the Mos1 mariner transposable element was altered by site-directed mutagenesis so that it exactly matched the nucleotide sequence of the right (3) ITR. The effects on the transposition frequency resulting from the use of two 3 ITRs, as well as those caused by the deletion of internal portions of the Mos1 element, were evaluated using plasmid-based transposition assays in Escherichia coli and Aedes aegypti. Donor constructs that utilized two 3 ITRs transposed with greater frequency in E. coli than did donor constructs with the wild-type ITR configuration. The lack of all but 10 bp of the internal sequence of Mos1 did not significantly affect the transposition frequency of a wild-type ITR donor. However, the lack of these internal sequences in a donor construct that utilized two 3 ITRs resulted in a further increase in transposition frequency. Conversely, the use of a donor construct with two 3 ITRs did not result in a significant increase in transposition in Ae. aegypti. Furthermore, deletion of a large portion of the internal Mos1 sequence resulted in the loss of transposition activity in the mosquito. The results of this study indicate the possible presence of a negative regulator of transposition located within the internal sequence, and suggest that the putative negative regulatory element may act to inhibit binding of the transposase to the left ITR. The results also indicate that host factors which are absent in E. coli, influence Mos1 transposition in Ae. aegypti.Communicated by G. P. Georgiev     

The mechanism of action of hexahydro-1,3,5-triethyl-s-triazine

Summary The mechanism of antimicrobial action of hexahydro-1,3,5-triethyl-s-triazine (HHTT) was studied using the HHTT-resistant isolate,Pseudomonas putida 3-T-15², its HHTT-sensitive, novobiocin-cured derivative,P. putida 3-T-15² 11:21,P. putida ATCC 12633,Pseudomonas aeruginosa PA01 andEscherichia coli J53 (RP4). HHTT was oxidized byP. putida 3-T-15², while respiration ofP. putida 3-T-15² 11:21 was inhibited by HHTT. Chemical assays showed that HHTT released formaldehyde.P. putida 3-T-15² was highly resistant to formaldehyde, whileP. putida 3-T-15² 11:21 was highly sensitive to formaldehyde. Both HHTT and formaldehyde acted similarly to inhibit proline uptake in bacterial cells and to inhibit the synthesis of the inducible enzymes, -galactosidase and glucose-6-phosphate dehydrogenase. HHTT did not have uncoupler-like activity.P. putida 3-T-15² used either HHTT or ethylamine, a component of HHTT, as a nitrogen source for growth, but neither HHTT, ethylamine or formaldehyde served as a carbon and energy source for growth. We concluded that a major mechanism of antimicrobial action of HHTT was through its degradation product, formaldehyde.     

The 41 carboxy-terminal residues of the miniF plasmid CcdA protein are sufficient to antagonize the killer activity of the CcdB protein

Summary The ccd operon of plasmid F encodes two genes, ccdA and ccdB, which contribute to the high stability of the plasmid by post-segregational killing of plasmid-free bacteria. The CcdB protein is lethal to bacteria and the CcdA protein is an antagonist of this lethal action. A 520 by fragment containing the terminal part of the ccdA gene and the entire ccdB gene of plasmid F was cloned downstream of the tac promoter. Although the CcdB protein was expressed from this fragment, no killing of host bacteria was observed. We found that the absence of killing was due to the presence of a small polypeptide, CcdA41, composed of the 41 C-terminal residues of the CcdA protein. This polypeptide has retained the ability to regulate negatively the lethal activity of the CcdB protein.     

Eine blütenmorphologische Analyse derLagoecieae (Apiaceae)

An analysis of the morphology, anatomy and ontogeny of the flowers, particularly of the gynoecium ofLagoecieae is presented. 1. The gynoecial model of angiosperms can be applied to all three generaArctopus, Lagoecia andPetagnia. 2. In the case ofArctopus an additional Apikalseptum is developed. 3. In the synascidiate region of the gynoecium the adaxial carpel is reduced inArctopus andPetagnia, the abaxial inLagoecia. 4. The reduced carpel produces either one mature ovule inArctopus, a rudimentary ovule inPetagnia, or none inLagoecia. 5.Petagnia andLagoecia have a completely pseudomonomerous gynoecium. 6.Arctopus displays many flower characteristics which lack in theSaniculoideae but occur in theHydrocotyloideae. 7. ForPetagnia andLagoecia an independent phylogenetic development within theSaniculoideae is assumed.

Herrn Univ.-Prof. Dr.Walter Leinfellner zum 70. Geburtstag gewidmet.     

Bristle patterns,clones and cell competition along the anterior margin ofNotch wings ofDrosophila hydei

Summary The bristle pattern along the anterior margin ofNotch (N1-22.3) wings ofDrosophila hydei and the occurrence ofyellow (y 1–38.8) marked clones induced by X-ray irradiation during various larval stages are described. UnirradiatedN/N ⁺ wings show gaps (notches) in the longitudinal bristle rows along the 1st longitudinal vein, with tufts of bristles particularly near gaps. X-ray irradiation increases the number and total length of the gaps. The patterning of bristles along the margin depends on theN ⁽⁺⁾ genotype of the induced clones. RecombinantN ⁺/N ⁺ clones from irradiated wings show excessive growth with an autonomous wildtype bristle pattern. Characteristically, these clones do not respect the dorso-ventral compartment boundary along the wing margin, do not follow an exponential (2ⁿ) growth pattern, tend to fill the gaps with bristles and theiryellow medial row bristles are less often interspersed withy ⁺ bristles than described forN ⁺/N ⁺ wings. HomozygousN appears to be a cell lethal condition inD. hydei as it is inD. melanogaster. When y clones were kept phenotypicallyNotch (viz.,N/N/N ⁺) as the background cells, we found a lower number ofy bristles, a lower percentage of mosaic wings but also a reltive deficiency ofy ⁺ interspersions. The latter is discussed in relation to a possible clonal originof the notches.     

A vital function for mitochondrial DNA in the petite-negative yeastKluyveromyces lactis

Petite-negative yeasts do not form viable respiratory-deficient mutants on treatment with DNA-targeting drugs that readily eliminate the mitochondial DNA (mtDNA) from petite-positive yeasts. However, in the petite-negative yeastKluyveromyces lactis, specific mutations in the nuclear genesMGI2 andMGI5 encoding the- and-subunits of the mitochondrial F₁-ATPase, allow mtDNA to be lost. In this study we show that wild-typeK. lactis does not survive in the absence of its mitochondrial genome and that the function ofmgi mutations is to suppress lethality caused by loss of mtDNA. Firstly, we find that loss of a multicopy plasmid bearing amgi allele readily occurs from a wild-type strain with functional mtDNA but is not tolerated in the absence of mtDNA. Secondly, we cloned theK. lactis homologue of theSaccharomyces cerevisiae mitochondrial genome maintenance geneMGM101, and disrupted one of the two copies in a diploid. Following sporulation, we find that segregants containing the disrupted gene form minicolonies containing 6-8000 inviable cells. By contrast, disruption ofMGM101 is not lethal in a haploidmgi strain with a specific mutation in a subunit of the mitochondrial F₁-ATPase. These observations suggest that mtDNA inK. lactis encodes a vital function which may reside in one of the three mitochondrially encoded subunits of F₀.     

Ultrastructure of the motile cells of the prostrate filamentous green algaeProtoderma sarcinoidea andChamaetrichon capsulatum

The biflagellate zoospores ofProtoderma sarcinoidea and the quadriflagellate zoospores ofChamaetrichon capsulatum are each covered by an amorphous, mucous material and a single layer of square scales, and the pyrenoid matrix is traversed by one or more thylakoid membranes. In the flagellar apparatus the basal bodies ofP. sarcinoidea and the upper basal bodies ofC. capsulatum are displaced in the counterclockwise absolute orientation, while the lower basal bodies ofC. capsulatum are directly opposed. Other components of the flagellar apparatus observed in each alga include: cruciately arranged d and s rootlets, each associated with an electron-dense component; simple terminal caps comprised of large and small subunits; a terminal electron-dense mass located near the proximal end of each basal body inP. sarcinoidea and near the upper basal bodies inC. capsulatum; and two rhizoplasts. Components specific to one or the other species include a single accessory basal body inP. sarcinoidea and a fibrous, electron-opaque band that links the upper and the lower basal bodies inC. capsulatum. The flagellar apparatus architecture ofP. sarcinoidea resemblesGayralia oxysperma, while that ofC. capsulatum is similar toTrichosarcina polymorphum andUlothrix species, all of which are included in theUlothrix-group,Ulotrichales, Ulvophyceae.     

Structural and functional analysis of the killer element pPin1-3 from Pichia inositovora

Strains of the yeast Pichia inositovora that carry the linear plasmids pPin1-1 (18 kb) and pPin1-3 (10 kb) display a killer activity towards Saccharomyces cerevisiae. Cloning and sequencing of the smaller plasmid, pPin1-3, revealed that it is 9683 bp long and has 154-bp terminal inverted repeats. Comparison of pPin1-3 with the only other completely sequenced killer plasmid, pGKL1 of Kluyveromyces lactis, revealed differences in genome organization. The Pichia element has four ORFs that account for 95% of the sequence. ORF1 is homologous to the putative immunity gene of the K. lactis system. A viral B-type DNA polymerase is encoded by ORF2. The predicted product of ORF3 displays similarities to the - and -subunits of the heterotrimeric K. lactis killer toxin, also known as zymocin. A cysteine-rich chitin-binding site and a chitinase signature, characteristic for the -subunit of zymocin were identified in Orf3p. Chitin affinity chromatography and Western analysis confirmed the plasmid specific expression and secretion of a protein that cross-reacts with an antibody raised against the -subunit of K. lactis zymocin. Disruption of the major chitin synthase-gene ( CHS3) renders S. cerevisiae resistant to the toxin, providing further evidence that chitin is the cellular receptor for the P. inositovora toxin. Orf4p of pPin1-3 displays only weak similarities to the -subunit of zymocin, which causes a G1 cell-cycle arrest in S. cerevisiae. However, disruption of the S. cerevisiae gene ELP3/TOT3, which encodes a histone-acetyltransferase that is essential for zymocin action, resulted in reduced sensitivity to the P. inositovora toxin also. Thus, despite obvious differences in genome organization and protein architecture, both killer systems very probably have similar modes of action.Communicated by C. P. Hollenberg     

ThehapC gene ofAspergillus nidulans is involved in the expression of CCAAT-containing promoters

The 5 regulatory region of theamdS gene ofAspergillus nidulans, which encodes an acetamidase required for growth on acetamide as a carbon and nitrogen source, contains a CCAAT sequence which is required for setting the basal level ofamdS expression. Mobility shift studies have identified a factor inA. nidulans nuclear extracts which binds to this CCAAT sequence. InSaccharomyces cerevisiae theHAP3 gene encodes one component of a multisubunit complex that binds CCAAT sequences. A search of the EMBL and SwissProt databases has revealed anA. nidulans sequence with significant homology to theHAP3 gene adjacent to the previously cloned regulatory geneamdR. Sequencing of the remainder of this region has confirmed the presence of a gene, designatedhapC, with extensive homology toHAP3. The predicted amino acid sequence of HapC shows extensive identity to HAP3 in the central conserved domain, but shows little conservation in the flanking sequences. A haploid carrying ahapC deletion has been created and is viable, but grows poorly on all media tested. This null mutant grows especially slowly on acetamide as a sole carbon and nitrogen source, indicating thathapC plays a role inamdS expression. In agreement with this notion, it has been shown that thehapC deletion results in reduced levels of expression of anamdS::lacZ reporter gene and this effect is particularly evident under conditions of carbon limitation. Nuclear extracts prepared from thehapC deletion mutant show no CCAAT binding activity to theamdS orgatA promoters, indicating thathapC may encode a component of the complex binding at this sequence.     

Behavior of organelle nuclei (nucleoids) in generative and vegetative cells during maturation of pollen inLilium longiflorum andPelargonium zonale

Summary The behavior of organelle nuclei during maturation of the male gametes ofLilium longiflorum andPelargonium zonale was examined by fluorescence microscopy after staining with 4,6-diamidino-2-phenylindole (DAPI) and Southern hybridization. The organelle nuclei in both generative and vegetative cells inL. longiflorum were preferentially degraded during the maturation of the male gametes. In the mature pollen grains ofL. longiflorum, there were absolutely no organelle nuclei visible in the cytoplasm of the generative cells. In the vegetative cells, almost all the organelle nuclei were degraded. However, in contrast to the situation in generative cells, the last vestiges of organelle nuclei in vegetative cells did not disappear completely. They remained in evidence in the vegetative cells during germination of the pollen tubes. InP. zonale, however, no evidence of degradation of organelle nuclei was ever observed. As a result, a very large number of organelle nuclei remained in the sperm cells during maturation of the pollen grains. When the total DNA isolated from the pollen or pollen tubes was analyzed by Southern hybridization with a probe that contained therbc L gene, for detection of the plastid DNA and a probe that contained thecox I gene, for detection of the mitochondrial DNA, the same results were obtained. Therefore, the maternal inheritance of the organelle genes inL. longiflorum is caused by the degradation of the organelle DNA in the generative cells while the biparental inheritance of the organelle genes inP. zonale is the result of the preservation of the organelle DNA in the generative and sperm cells. To characterize the degradation of the organelle nuclei, nucleolytic activities in mature pollen were analyzed by an in situ assay on an SDS-DNA-gel after electrophoresis. The results revealed that a 40kDa Ca²⁺-dependent nuclease and a 23 kDa Zn²⁺ -dependent nuclease were present specifically among the pollen proteins ofL. longiflorum. By contrast, no nucleolytic activity was detected in a similar analysis of pollen proteins ofP. zonale.     

Highly efficient integration of foreign DNA into the genome of the green sulfur bacterium,Chlorobium vibrioforme by homologous recombination

Highly efficient and reproducible transformation ofChlorobium vibrioforme with plasmid DNA has been achieved by electroporation. Specific parameters have been optimized for the electrotransformation procedure. The method was developed using a construct containing a full copy of thepscC gene encoding the cytochromec ₅₅₁ subunit of the photosynthetic reaction center complex and theaadA gene encoding streptomycin resistance as selectable marker. Southern blotting analysis showed that the tested colonies were true transformants with the plasmid integrated into the genome by single homologous recombination. No transformants were obtained using the vector without thepscC gene showing that this vector does not replicate inC. vibrioforme. Thus transformation is possible only by homologous recombination. When using constructs designed to inactivate thepscC gene by insertion no transformants were obtained, indicating that the gene is indispensable for growth. The vector pVS2 carrying genes for erythromycin and chloramphenicol resistance was shown to replicate inC. vibrioforme. The two transformations shown here, provide an important genetical tool in the further analysis of structure and function of the photosynthetic apparatus in green sulfur bacteria.     

Competitive growth of slow growingRhizobium japonicum against fast growingEnterobacter andPseudomonas species at low concentrations of succinate and other substrates in dialysis culture

A cultivation system with simultaneous growth of six bacterial cultures in separate bags in dialysis culture was developed. In a medium with no added carbon source (one half concentrated Hoagland solution, water deionized and distilled), cell number ofRhizobium japonicum increased during a 7 day period by a factor of 35, whereas the number ofEnterobacter aerogenes cells decreased to one half. With a concentration of 100 nM succinate as an additional carbon source in the inflow,Rhizobium japonicum 61-A-101 cell number increased by a factor of 50 during an 8 day period, whereas cell number ofEnterobacter cloacae NCTC 10005 only doubled and ofEnterobacter aerogenes NCTC 10006 decreased. At 10 mM concentration of succinate in the inflow, doubling time the twoEnterobacter strains was about 12 h, compared to about 24 h for theRhizobium japonicum strain. Varying the succinate concentration from 10 mM to 100 nM in the inflow,Rhizobium japonicum 61-A-101 surpassed theEnterobacter aerogenes strains in the growth rate between 1 mM and 100 M succinate in the inflowing medium. Three otherRhizobium japonicum strains (fix⁺ and fix^-) did grow with a similar rate as strain 61-A-101 at very low concentrations of substrate. Growth rates for the strains were confirmed by protein data per culture. Growing in competition with twoPseudomonas strains,Rhizobium japonicum RH 31 Marburg (fix^-) did overgrow alsoPseudomonas fluorescens, was however outgrown byPseudomonas putida. In utilizing low concentrations of a¹⁴C labelled organic acid (malonate), three strains ofRhizobium japonicum left 2–4 times smaller amounts of¹⁴C in the medium than two species ofPseudomonas and two species ofArthrobacter.On sabbatical leave at ANU     

The suppressor of Hairy-wing binding region is required for gypsy mutagenesis

Summary We undertook a deletional analysis of the gypsy retrotransposon in order to determine which sequences of the element are required for its mutagenic effect. We show that a phenotype indistinguishable from that ofy ² flies can be generated by transformingy ^– flies with a construct containing theyellow gene and a gypsy element located at the same insertion site inyellow as found iny ² flies. When flies are transformed with similar constructs in which increasing amounts of the 5 transcribed untranslated region of gypsy have been removed, either a partialy ² revertant or a completely revertant phenotype is obtained. These results yield direct proof that the region of gypsy to which thesu(Hw) protein binds is required for the generation of mutant phenotypes by this retrotransposon.