Transformed bacterial symbionts re-introduced to and detected in host gut

Strains of Enterobacter agglomerans and Klebsiella pneumoniae isolated from Rhagoletis completa Cresson were engineered to express transgenic fluorescent proteins (ECFP, DsRed). These bacteria were introduced into flies by feeding the flies a sucrose solution in which the bacteria were suspended. The transgenic and heterologous marker protein was expressed and visible in the bacteria after they were ingested by WHF and while they were in the fly gut. We describe the plasmids used to transform these bacteria and demonstrate expression of heterologous proteins from the transforming plasmids and discuss the implications for future pest control strategies. Received: 14 September 2001 / Accepted: 22 October 2001     

Diversity of nif gene location and nitrogen fixation among root-associated Enterobacter and Klebsiella strains

Our previous work showed that strains of dinitrogen fixing enterobacter and Klebsiella were found associated with the roots of uncultivated grasses in Finland more commonly than other species of diazotrophic bacteria. In this paper we compare E. agglomerans strains to K. pneumoniae and K. terrigena strains, and show that the E. agglomerans strains fall into two biogroups. The groups differ not only in the utilization of different carbon sources and other physiological characteristics such as the production of indole, but also in the physiology and genetics of nitrogenase activity. Biotype 1 (isolated from Achillea millefolium, Calamagrostis arundinacea, and Phleum pratense) showed active nitrogenase in atmospheric oxygen, whereas biotype 2 (from Phalaris arundinacea) resembled K. pneumoniae in that it was active at reduced oxygen pressure (pO₂<-0.002) only. DNA of all strains showed positive hybridization with K. pneumoniae nifHDK genes (pSA30) but differed in the location of the genes. Biotype 1 strains of E. agglomerans carried nifHDK genes on large (105–125 Mdal) plasmids, whereas no plasmid was detected in biotype 2 or in the K. pneumoniae strains isolated from Agrostis stolonifera and Poa pratensis and K. terrigena strain isolated from Carex pallescens. The one K. terrigena strain (isolated from Ph. arundinacea) that was found to contain an indigenous plasmid (80 Mdal) did not carry nifHDK genes on this plasmid.     

Efficient germ-line transformation of the economically important pest species Lucilia cuprina and Lucilia sericata (Diptera, Calliphoridae)

The green blowfly species Lucilia cuprina and Lucilia sericata are economically important pests for the sheep industries of Australia and New Zealand. L. cuprina has long been considered a good target for a genetic pest management program. In addition, L. sericata maggots are used in the cleaning of wounds and necrotic tissue of patients suffering from ulcers that are difficult to treat by other methods. Development of efficient transgenesis methods would greatly facilitate the development of strains ideal for genetic control programs or could potentially improve “maggot therapy”. We have previously reported the germ-line transformation of L. cuprina and the design of a “female killing system” that could potentially be applied to this species. However, the efficiency of transformation obtained was low and transformed lines were difficult to detect due to the low expression of the EGFP marker used. Here we describe an efficient and reliable method for germ-line transformation of L. cuprina using new piggyBac vector and helper plasmids containing the strong promoter from the L. cuprina hsp83 gene to drive expression of the transposase and fluorescent protein marker gene. We also report, for the first time, the germ-line transformation of L. sericata using the new piggyBac vector/helper combination.     

The mechanics of bacterial cluster formation on plant leaf surfaces as revealed by bioreporter technology

Bacteria that colonize the leaves of terrestrial plants often occur in clusters whose size varies from a few to thousands of cells. For the formation of such bacterial clusters, two non‐mutually exclusive but very different mechanisms may be proposed: aggregation of multiple cells or clonal reproduction of a single cell. Here we assessed the contribution of both mechanisms on the leaves of bean plants that were colonized by the bacterium Pantoea agglomerans. In one approach, we used a mixture of green and red fluorescent P. agglomerans cells to populate bean leaves. We observed that this resulted in clusters made up of only one colour as well as two‐colour clusters, thus providing evidence for both mechanisms. Another P. agglomerans bioreporter, designed to quantify the reproductive success of bacterial colonizers by proxy to the rate at which green fluorescent protein is diluted from dividing cells, revealed that during the first hours on the leaf surface, many bacteria were dividing, but not staying together and forming clusters, which is suggestive of bacterial relocation. Together, these findings support a dynamic model of leaf surface colonization, where both aggregative and reproductive mechanisms take place. The bioreporter‐based approach we employed here should be broadly applicable towards a more quantitative and mechanistic understanding of bacterial colonization of surfaces in general.     

Transgenic oat plants via visual selection of cells expressing green fluorescent protein

 New selectable markers and selection systems are needed to increase the efficiency and flexibility of plant transformation. The objective of this research was to determine if the green fluorescent protein (gfp) gene could be utilized as a visual selectable marker for transformation of oat (Avena sativa L.). A modified gfp gene was delivered into oat cells by microprojectile bombardment. Cell clusters expressing gfp were visually identified using fluorescence microscopy and physically isolated at each subculture. Eleven independent transgenic cell lines were obtained, and fertile plants regenerated from all lines. Transgene integration and expression were confirmed in transgenic plants and progeny. Transgene expression segregated in a 3 : 1 ratio in progeny of the majority of the transgenic lines. Received: 11 May 1999 / Revision received: 31 August 1999 / Accepted: 2 September 1999     

An alternative method for the genetic transformation of sweet organce

Summary An alternative method for transforming sweet organe [Citrus sinensis (L.) Osbeck] has been developed. Plasmid DNA encoding the non-destructive selectable marker enhanced green fluorescent protein gene was introduced using polyethylene glycol into protoplasts of ‘Itaborai’ sweet organe isolated from an embryogenic nucellar-derived suspension culture. Following protoplast culture in liquid medium and transfer to solid medium, transformed calluses were identified via expression of the green fluorescent protein, physically separated from non-transformed tissue, and cultured on somatic embryogenesis induction medium. Transgenic plantlets were recovered from germinating somatic embryos and by in vitro rooting of shoots. To expedite transgenic plant recovery, regenerated shoots were also micrografted onto sour orange seedling rootstocks. Presence of the transgene in calluses and regenerated sweet organe plants was verified by gene amplification and Southern analyses. Potential advantages of this transformation system over the commonly used Agrobacterium methods for citrus are discussed.     

Rhizome-associated bacterial communities of healthy and declining reed stands in Lake Velencei,Hungary

Lake Velencei is a shallow soda lake with extensive reed coverage. In this study, the bacterial communities of reed (Phragmites australis (Cav.) Trin. ex Steudel) rhizomes from healthy and declining stands were compared. Inner and outer rhizome surfaces were sampled. Samples were plated and isolated in September 1998 and June 1999. Phenotypic data of 371 bacterial strains were used for cluster analysis. Identification of phena was based on partial 16S rDNA sequence analysis of representative strains. Healthy reed stand rhizomes in fall 1998 were dominantly colonised by facultatively fermentative organisms, like Erwinia billingiae, Aeromonas sobria, Pantoea agglomerans, and Pseudomonas azotoformans. In the June 1999 sample, mainly Kocuria rosea and various Bacillus spp. dominated. In declining stands of September 1998, a saprotrophic community was found: Acinetobacter spp., Aeromonas hydrophila, Curtobacterium luteum, Agrobacterium vitis, and two further groups representing presumably new taxa. In June 1999, reed rhizomes were colonised by Kocuria rosea, but Dietzia maris and Bacillus cohnii could be isolated as well. Healthy and declining reed stand rhizomes can be distinguished based on the culturable bacterial community. No obligately plant pathogenic bacteria were found, however the possibility of a local, opportunistic bacterial invasion can not be ruled out (e.g. Curtobacterium). The presence of potentially beneficial bacterial species was demonstrated in the healthy reed rhizome rhizosphere (e.g. Pseudomonas azotoformans, Pantoea agglomerans).

     

Characteristics of natural strains of naphthalene-utilizing bacteria of the genus <Emphasis Type="Italic">Pseudomonas</Emphasis>

Sixty-three strains of bacteria capable of utilizing naphthalene as the sole source of carbon and energy were isolated from 137 samples of soil taken in different sites in Belarus. All isolated bacteria contained extrachromosomal genetic elements of 45 to 150 kb in length. It was found that bacteria of 31 strains contained the IncP-9 incompatibility group plasmids, bacteria of one strain carried a plasmid containing replicons IncP-9 and IncP-7, and bacteria of 31 strains contained unidentified plasmids. Primary identification showed that the hosts of plasmids of naphthalene biodegradation are fluorescent bacteria of the genus Pseudomonas (P. putida and P. aeruginosa; a total of 47 strains) and unidentified nonfluorescent microorganisms (a total of 16 strains). In addition to the ability to utilize naphthalene, some strains exhibited the ability to stimulate the growth and development of the root system of Secale cereale.Translated from Izvestiya Akademii Nauk, Seriya Biologicheskaya, No. 2, 2005, pp. 162–167.Original Russian Text Copyright © 2005 by Levchuk, Vasilenko, Bulyga, Titok, Thomas.     

Immunolocalization of Dinitrogenase Reductase Produced by Klebsiella pneumoniae in Association with Zea mays L.

The endophytic lifestyle of Klebsiella pneumoniae is described, including the production of dinitrogenase reductase by bacteria residing in maize root tissue. The green fluorescent protein (GFP) was used to detect the colonization of maize by K. pneumoniae strains 2028 and 342. These strains were found to reside in intercortical layers of the stem and within the region of maturation in the root. The production of dinitrogenase reductase by GFP-tagged bacteria was visualized using immunolocalization. This activity was only apparent when bacteria were supplied with an exogenous carbon source. The results suggest that maize provides a suitable habitat for K. pneumoniae and that this species is capable of producing nitrogenase under the appropriate plant cultivation conditions.     

Plasmids in Vibrio parahemolyticus Strains Isolated in Japan and Bangladesh with Special Reference to Different Distributions

We surveyed plasmids in naturally occurring Vibrio parahemolyticus strains isolated in Japan and Bangladesh. Among the strains isolated in Japan, about half of the strains isolated from stools of patients of domestic diarrhea outbreaks as well as of travelers returning from East Asia were found to have plasmids, but no strains from foods had plasmids. In contrast, among the strains isolated in Bangladesh, none of the four strains isolated from patients had plasmids, but two out of eight strains isolated from water had plasmids, suggesting that plasmids are common in strains from the water in Bangladesh. All plasmids so far reported in V. parahemolyticus were detected in strains isolated from stools of patients. Incidences of plasmids in this organism were not so high in either area. In Japan, all plasmids were detected in strains from human intestines at 37 C, but in Bangladesh, where the temperature is around 30–40 C, the plasmids were detected in strains from the natural environment. These results suggested the possibility that these plasmids can come from different bacteria under rather high temperatures and that incidences of plasmids are influenced by the incidences of plasmids in bacteria present in the vicinity of V. parahemolyticus strains. None of these plasmids were found to have any relation to the biological characters tested.     

Virulence of Klebsiella pneumoniae Isolates Harboring bla KPC-2 Carbapenemase Gene in a Caenorhabditis elegans Model

Klebsiella pneumoniae carbapenemase (KPC) is a carbapenemase increasingly reported worldwide in Enterobacteriaceae. The aim of this study was to analyze the virulence of several KPC-2-producing K. pneumoniae isolates. The studied strains were (i) five KPC-2 clinical strains from different geographical origins, belonging to different ST-types and possessing plasmids of different incompatibility groups; (ii) seven transformants obtained after electroporation of either these natural KPC plasmids or a recombinant plasmid harboring only the bla _KPC-2 gene into reference strains K. pneumoniae ATCC10031/{"type":"entrez-protein","attrs":{"text":"CIP53153","term_id":"878514309","term_text":"CIP53153"}}CIP53153; and (iii) five clinical strains cured of plasmids. The virulence of K. pneumoniae isolates was evaluated in the Caenorhabditis elegans model. The clinical KPC producers and transformants were significantly less virulent (LT50: 5.5 days) than K. pneumoniae reference strain (LT50: 4.3 days) (p<0.01). However, the worldwide spread KPC-2 positive K. pneumoniae ST258 strains and reference strains containing plasmids extracted from K. pneumoniae ST258 strains had a higher virulence than KPC-2 strains belonging to other ST types (LT50: 5 days vs. 6 days, p<0.01). The increased virulence observed in cured strains confirmed this trend. The bla _KPC-2 gene itself was not associated to increased virulence.     

Interspecific plasmid transfer between Streptococcus pneumoniae and Bacillus subtilis

Summary The streptococcal plasmids pMV158 and pLS1, grown in Streptococcus pneumoniae, were transferred to Bacillus subtilis by DNA-mediated transformation. The plasmids were unchanged in the new host; no deletions were observed in 80 instances of transfer. Their copy number was similar to that in S. pneumoniae. Two B. subtilis plasmids, pUB110 and pBD6, could not be transferred to S. pneumoniae. Hybrid plasmids were produced by recombining the EcoRI fragment of pBD6 that confers Km^r with EcoRI-cut pLS1, which confers Tc^r. The simple hybrid, pMP2, was transferable to both species and expressed Tc^r and Km^r in both. A derivative, pMP5, which contained an insertion in the pBD6 component, expressed a higher level of kanomycin resistance and was more easily selected in S. pneumoniae. Another derivative, pMP3, which contained an additional EcoRI fragment, presumably of pneumococcal chromosomal DNA, could not be transferred to B. subtilis. Previous findings that monomeric plasmid forms could transform S. pneumoniae but not B. subtilis were confirmed using single plasmid preparations. Although plasmids extracted from either species were readily transferred to S. pneumoniae, successive passage in B. subtilis increased the ability of plasmid extracts to transfer the plasmid to a B. subtilis recipient. This adaptation was tentatively ascribed to an enrichment of multimeric forms in extracts of B. subtilis as compared to S. pneumoniae. A review of host ranges exhibited by plasmids of Gram-positive bacteria suggested differences in their ability to use particular host replication functions. The pMP5 plasmid, with readily selectable Km^r and Tc^r markers in both hosts, and with the potential for inactivation of Km^r by insertion in the Bg/II site, could be a useful shuttle vector for cloning in S. pneumoniae and B. subtilis.     

野生鸟类分离的多重耐药肺炎克雷伯氏菌(Klebsiella pneumoniae)耐药基因分子进化特征研究

【目的】调查野生鸟类携带菌的耐药状况,探索其在细菌耐药性传播过程中的作用。【方法】从野生鸟类石鸡、绯胸鹦鹉、太阳锥尾鹦鹉和黑领椋鸟的新鲜粪便分离4株Klebsiella pneumoniae,采用微量肉汤稀释法评估其多重耐药表型,并利用全基因组测序技术和细菌全因组关联分析、比较基因组学方法对分离株进行分子溯源,系统解析其携带的多重耐药质粒或基因与其宿主、同源质粒间的关联。【结果】4株肺炎克雷伯菌的耐药谱各不相同,来自石鸡样本的分离株S90-2对9种药物耐受,绯胸鹦鹉样本分离株S141对3种药物耐受,太阳锥尾鹦鹉分离株M911-1仅耐受氨苄西林,黑领椋鸟的样本分离株S130-1对所使用的14种药物完全敏感。S90-2属于ST629型,携带bla_CTX-M-14、fosA6、aac(3)-Iid和bla_SHV-11为主的30个耐药基因和携带1个耐药性质粒pS90-2.3 (IncR型)。S141属于ST1662型,携带fosA5、bla_SHV-217等27个耐药基因,1个质粒pS141.1 [IncFIB(K)(pCAV1099-114)/repB型]仅携带耐药基因adeF。M911-1为新ST类型,携带bla_SHV-1、fosA6等共计27个耐药基因,其质粒pM911-1.1携带了3个耐药基因。S130-1属于ST3753型,携带bla_SHV-11、fosA6等27个耐药基因,pS130-1 [IncFIB(K)型]则仅携带一个耐药基因tet(A)。质粒比对表明,质粒pS90-2.3携带的耐药基因片段源自不同的肠杆菌科菌株染色体或质粒。pS90-2.3的同源质粒主要来自人类宿主菌,且主要在中国分布,这些质粒主要细菌宿主为K. pneumoniae和Escherichia coli,且ST11型K. pneumoniae分离株为重要宿主菌。【结论】本研究中来自野生鸟类的多重耐药K. pneumoniae,其耐药基因主要来自质粒,质粒耐药基因主要由转座子、插入序列、整合子和前噬菌体等可移动元件介导,这些多重耐药质粒与人类的宿主菌密切相关。     

Characterization of Streptococcus pneumoniae N-acetylglucosamine-6-phosphate deacetylase as a novel diagnostic marker

The identification of novel diagnostic markers of pathogenic bacteria is essential for improving the accuracy of diagnoses and for developing targeted vaccines. Streptococcus pneumoniae is a significant human pathogenic bacterium that causes pneumonia. N-acetylglucosamine-6-phosphate deacetylase (NagA) was identified in a protein mixture secreted by S. pneumoniae and its strong immunogenicity was confirmed in an immuno-proteomic assay against the anti-serum of the secreted protein mixture. In this study, recombinant S. pneumoniae NagA protein was expressed and purified to analyze its protein characteristics, immunospecificity, and immunogenicity, thereby facilitating its evaluation as a novel diagnostic marker for S. pneumoniae. Mass spectrometry analysis showed that S. pneumoniae NagA contains four internal disulfide bonds and that it does not undergo post-translational modification. S. pneumoniae NagA antibodies successfully detected NagA from different S. pneumoniae strains, whereas NagA from other pathogenic bacteria species was not detected. In addition, mice infected with S. pneumoniae generated NagA antibodies in an effective manner. These results suggest that NagA has potential as a novel diagnostic marker for S. pneumoniae because of its high immunogenicity and immunospecificity.     

Distribution and Replication of the Pathogenicity Plasmid pPATH in Diverse Populations of the Gall-Forming Bacterium Pantoea agglomerans

Pantoea agglomerans has been transformed from a commensal bacterium into two related gall-forming pathovars by acquisition of pPATH plasmids containing a pathogenicity island (PAI). This PAI harbors an hrp/hrc gene cluster, type III effectors, and phytohormone biosynthetic genes. DNA typing by pulsed-field gel electrophoresis revealed two major groups of P. agglomerans pv. gypsophilae and one group of P. agglomerans pv. betae. The pPATH plasmids of the different groups had nearly identical replicons (98% identity), and the RepA protein showed the highest level of similarity with IncN plasmid proteins. A series of plasmids, designated pRAs, in which the whole replicon region (2,170 bp) or deleted derivatives of it were ligated with nptI were generated for replicon analysis. A basic 929-bp replicon (pRA6) was sufficient for replication in Escherichia coli and in nonpathogenic P. agglomerans. However, the whole replicon region (pRA1) was necessary for expulsion of the pPATH plasmid, which resulted in the loss of pathogenicity. The presence of direct repeats in the replicon region suggests that the pPATH plasmid is an iteron plasmid and that the repeats may regulate its replication. The pPATH plasmids are nonconjugative but exhibit a broad host range, as shown by replication of pRA1 in Erwinia, Pseudomonas, and Xanthomonas. Restriction fragment length polymorphism analyses indicated that the PAIs in the two groups of P. agglomerans pv. gypsophilae are similar but different from those in P. agglomerans pv. betae. The results could indicate that the pPATH plasmids evolved from a common ancestral mobilizable plasmid that was transferred into different strains of P. agglomerans.     

In Vivo Cloning of Arylsulfatase-Tyramine Oxidase Genes in rec Strains of Klebsiella aerogenes

A general, genetic technique for in vivo cloning of bacterial genes is presented. We previously introduced the Mu phage into various genera of bacteria including Klebsiella aerogenes with RP4 : : Mu. Using these strains carrying RP4 : : Mu cts and thermo-inducible Mu prophage in the chromosome, we cloned in vivo the arylsulfatase (ats) and tyramine oxidase (tyn) genes by partial thermo-induction. The donor strains carrying the recombinant plasmids were conjugated with K. aerogenes rec strains, which were isolated as UV-sensitive mutants. The resultant recombinant plasmids, pAT1 and pAT2, were purified and used for the transformation of mutant strains deficient in the ats and tyn genes. The ats-tyn genes seemed to be transposed into the RP4::Mu cts plasmid together with other chromosomal DNA fragments. This in vivo cloning method is applicable to a wide variety of gram-negative bacteria.     

Tools for chloroplast transformation in Chlamydomonas: expression vectors and a new dominant selectable marker

Reverse-genetic studies of chloroplast genes in the green alga Chlamydomonas reinhardtii have been hampered by the paucity of suitable selectable markers for chloroplast transformation. We have constructed a series of vectors for the targeted insertion and expression of foreign genes in the Chlamydomonas chloroplast genome. Using these vectors we have developed a novel selectable marker based on the bacterial gene aphA-6, which encodes an aminoglycoside phosphotransferase. The aphA-6 marker allows direct selection for transformants on medium containing either kanamycin or amikacin. The marker can be used to inactivate or modify specific chloroplast genes, and can be used as a reporter of gene expression. The availability of this marker now makes possible the serial transformation of the chloroplast genome of Chlamydomonas. Received: 26 October 1999 / Accepted: 28 December 1999     

Aggregates of Resident Bacteria Facilitate Survival of Immigrant Bacteria on Leaf Surfaces

The fate of immigrant bacterial cells on leaves under stressful conditions was determined as a function of the anatomical features and the local spatial density of resident cells at their landing site. Pantoea agglomerans 299R was established on bean leaves and the survival of immigrant cells of Pseudomonas fluorescens A506 and Pseudomonas syringae B728a, as well as P. agglomerans itself, was determined by epifluorescence microscopy following subsequent exposure of plants to desiccation stress. Resident and immigrant bacterial strains constitutively expressed the cyan and the green fluorescent protein, respectively, and the viability of individual cells was assessed directly on leaf surfaces following propidium iodide staining. Although only a small fraction of the immigrant cells landed on established bacterial aggregates, their fate was usually strongly influenced by the presence of indigenous bacteria at the site at which they landed. Immigrants of P. agglomerans 299R or P. fluorescens A506 that arrived as solitary cells had about double the probability of survival when landing on aggregates formed by P. agglomerans 299R than when landing on uncolonized areas of the leaf surface. In contrast, the survival of P. syringae B728a was similar irrespective of whether it landed on colonized or uncolonized parts of a leaf. The nature of plant anatomical features at which immigrant bacteria landed also strongly influenced the fate of immigrant bacteria. The fraction of immigrant cells of each species tested that landed on veins, glandular trichomes, or epidermal cells altered by P. agglomerans that died was always less than when they landed on normal epidermal cells or at the base of hooked trichomes. Depending on the process by which immigrants arrive at a leaf, only a small fraction of cells may be deposited on existing bacterial aggregates. Although uncolonized sites differed greatly in their ability to influence the survival of immigrant cells, the fate of an immigrant bacterium will depend on the nature of the leaf structure on which it is deposited, and apparently indirectly on the amount of nutrients and water available at that site to support the development of bacterial aggregates.     

Development and use of a piggyBac‐based jumpstarter system in Drosophila suzukii

Spotted wing drosophila, Drosophila suzukii, is an invasive pest that primarily attacks fresh, soft‐skinned fruit. Although others have reported successful integration of marked piggyBac elements into the D. suzukii genome, with a very respectable transgenesis rate of ～16%, here we take this work a step further by creating D. suzukii jumpstarter strains. These were generated through integration of a fluorescent‐marked Minos element carrying a heat shock protein 70‐driven piggyBac transposase gene. We demonstrate that there is a dramatic increase in transformation rates when germline transformation is performed in a transposase‐expressing background. For example, we achieved transformation rates as high as 80% when microinjecting piggyBac‐based plasmids into embryos derived from one of these D. suzukii jumpstarter strains. We also investigate the effect of insert size on transformation efficiency by testing the ability of the most efficient jumpstarter strain to catalyze integration of differently‐sized piggyBac elements. Finally, we demonstrate the ability of a jumpstarter strain to remobilize an already‐integrated piggyBac element to a new location, demonstrating that our jumpstarter strains could be used in conjunction with a piggyBac‐based donor strain for genome‐wide mutagenesis of D. suzukii.     

A New Primer Pair for Detection of Chlamydia pneumoniae by Polymerase Chain Reaction

In order to improve the detection and identification of Chlamydia pneumoniae, new primers for polymerase chain reaction (PCR) were designed based on the DNA base sequence within the 53-kDa protein gene, which is specific for C. pneumoniae. The primers permitted the identification of 24 C. pneumoniae strains collected from different geographical locations, but no reaction was observed with C. trachomatis, C. psittaci nor C. pecorum. The primers were unable to amplify the DNA of bacteria commonly related to respiratory tract infections. The positive amplification was achieved with only 9 EBs/assay. Therefore, the new primers seem to be useful in the diagnosis of C. pneumoniae infections.