Molecular characterization of methicillin-resistant <Emphasis Type="Italic">Staphylococcus aureus</Emphasis> nasal isolates from Turkey

Methicillin-resistant Staphylococcus aureus (MRSA) colonize most frequently in the anterior nares of the nose and cause serious infections all over the world. The aim of this study was to determine the nasal carriage rate of S. aureus and MRSA strains in Turkish elementary school children. We also analyzed molecular characterizations of MRSA strains by using pulse field gel electrophoresis (PFGE), multi locus sequence typing (MLST), staphylococcal chromosomal cassette mec (SCCmec) typing, and detection of the Panton-valentine leucocidin (PVL) gene. The nasal swabs were obtained from 4,050 children during a 4 month period in Ankara. In vitro antimicrobial susceptibility testing to 1 μg oxacillin and 30 μg cefoxitin was determined by a disk diffusion method. We found that the 1,001 of 4,050 (24.7%) children were colonized with S. aureus. Three S. aureus strains were resistant to oxacillin and cefoxitin. The rate of MRSA among all children was 0.07%. The MRSA strains revealed three different PFGE pattern. All MRSA isolates by harbored the SCCmec type IV element, but not the PVL gene. The two MRSA isolate belonged to sequence type (ST) 30, whereas the other one was a unique type. The results of this study demonstrated that S. aureus nasal carriage rate was consistent with previous studies. However, MRSA carriage rate was low. This study also indicated that the ST30-type IV without PVL gene MRSA clone may be expected to spread in Turkish community.     

Community and hospital acquired methicillin resistant <Emphasis Type="Italic">Staphylococcus aureus</Emphasis> efficiently retain the <Emphasis Type="Italic">Van A</Emphasis> determinant

Dissemination of vancomycin resistance from hospital to community strains is a serious threat to public health. Our study aimed to provide evidence for transmission of Van A type resistance from the hospital to the community. Wild-type community and hospital associated methicillin resistant Staphylococcus aureus strains were studied in vitro and in a model that mimicked a natural environment to ascertain their ability to acquire and maintain the vancomycin resistance determinant (Van A gene) from vancomycin resistant Enterococcus faecalis. Fitness was assessed and the cost of Van A acquisition and retention was estimated. In vitro mating experiments were carried out using a filter mating technique and a model of a natural water body environment. Transfer of resistance was carried out in two different conditions: restricted and favorable. Transconjugants were confirmed by E test and PCR using specific primer sets. Growth kinetics and fitness measurements were done by spectrometric analysis. Using the in vitro filter mating technique, high transfer frequencies that ranged from 0.7 × 10^–3(0.0006) to 3.1 × 10^–4(0.00011) were recorded, with the highest transfer frequencies for CA MRSA (thermosensitively homogenous) (0.7 × 10^–3), and 1.2 × 10^–4 to 2.4 × 10^–6 in the model. HA MRSA (homogenous) showed a greater capacity (3.6 × 10^–4) to receive the Van A gene, while CA MRSA showed a reduced ability to maintain the gene after serial subcultures. CA and HA thermosensitively heterogeneous MRSA transconjugants exhibited higher growth rates. The present study provides evidence for the enhanced ability of CA and HA MRSA clones to acquire and maintain Van A type resistance.     

<Emphasis Type="Italic">Sporidiobolus johnsonii</Emphasis> and <Emphasis Type="Italic">Sporidiobolus salmonicolor</Emphasis> revisited

The relationship between Sporidiobolus johnsonii and S. salmonicolor was investigated using rDNA sequence data. Two statistically well-supported clades were obtained. One clade included the type strain of S. johnsonii and the other included the type strain of S. salmonicolor. However, some mating strains of S. salmonicolor were found in the S. johnsonii group. These strains belonged to mating type A2 and were sexually compatible with mating type A1 strains from the S. salmonicolor group. DNA–DNA reassociation values were high within each clade and moderate between the two clades. In the re-investigation of teliospore germination, we observed that the basidia of S. salmonicolor were two-celled. In S. johnsonii, basidia were not formed and teliospore germination resulted in direct formation of yeast cells. We hypothesize that the S. johnsonii clade is becoming genetically isolated from the S. salmonicolor group and that a speciation process is presently going on. We suspect that the observed sexual compatibility between strains of the S. johnsonii and S. salmonicolor groups and the possible genetic flow between the two species has little biological relevance because distinct phenotypes have been fixed in the two taxa and intermediate (hybrid) sequences for LSU and ITS rDNAs have not been detected.     

Typing of Staphylococcal Cassette Chromosome <Emphasis Type="Italic">mec</Emphasis> Encoding Methicillin Resistance in <Emphasis Type="Italic">Staphylococcus aureus</Emphasis> Strains Isolated at the Bone Marrow Transplant Centre of Tunisia

Staphylococcal Cassette Chromosome mec (SCCmec) is a mobile genetic element that carries the gene mecA mediating the methicillin resistance in staphylococci. It is composed of mec and ccr gene complexes. Six SCCmec types have been defined so far. SCCmec typing of 13 methicillin-resistant Staphylococcus aureus (MRSA) out of 72 (18%) non redundant S. aureus strains recovered in 1998–2007 at the Bone Marrow Transplant Centre of Tunis was carried out. The isolates were identified by conventional methods. Antibiotic susceptibility was determined by oxacillin and cefoxitin disks and oxacillin MIC by E-test. Methicillin resistance was detected by mecA PCR. The SCCmec complex types were determined by PCR. The epidemiology of MRSA has been investigated by PFGE. Among 13 mecA positive strains, 12 were resistant to oxacillin (MIC = 3 to >256 μg/μl) and to cefoxitin and one strain was pre-resistant: susceptible to oxacillin (MIC = 0.19 μg/μl) and to cefoxitin. Hospital-acquired MRSA (HA-MRSA) strains had essentially SCCmec type IV (nine strains) or III (two strains) or I (one strain). One strain shown to carry ccrAB1 and ccrAB2 genes in combination with class B mec. Seven of 13 MRSA strains isolated from 2000 to 2006 were classified with major similarity group A harbored SCCmec type IV.     

Class 2 Integrons Dissemination Among Multidrug Resistance (MDR) Clones of <Emphasis Type="Italic">Acinetobacter baumannii</Emphasis>

Acinetobacter baumannii has emerged as a serious problem in the hospital environment at a global scale. Previous results from our laboratory showed a high frequency of class 2 integrons in A. baumannii strains from Argentina regarding the low rate of this element in A. baumannii isolates from the rest of the world. To reveal the current epidemiology of class 2 integrons, a molecular surveillance analyzing 78 multidrug resistant (MDR) A. baumannii isolates from Argentina and Uruguay was performed, exposing the presence of class 2 integron in the 36.61% of the isolates. Class 2 integron characterization showed that the typical Tn7::In2-7 array was present in 26 out of 27 intI2 positive isolates. All intI2 positive isolates contained at least one of the Tn7 transposition genes. In addition, we identified that 18 intI2 positive isolates possessed the Tn7::In2-7 within the attTn7 site. The molecular typing evidenced that clones I and IV that do not belong to widespread European clones I and II were found among the intI2 positive isolates. Our results exposed the widely dissemination of class 2 integron among MDR A. baumannii isolates from Argentina and Uruguay, also showing the persistence of two novel clones in our region, which could explain in part the high frequency of class 2 integron found in our region.     

Inverse PCR for subtyping of <Emphasis Type="Italic">Acinetobacter baumannii</Emphasis> carrying IS<Emphasis Type="Italic">Aba</Emphasis>1

Acinetobacter baumannii has been prevalent in nosocomial infections, often causing outbreaks in intensive care units. ISAba1 is an insertion sequence that has been identified only in A. baumannii and its copy number varies among strains. It has been reported that ISAba1 provides a promoter for bla_OXA-51-like, bla_OXA-23-like, and bla_ampC, which are associated with the resistance of A. baumannii to carbapenems and cephalosporins. The main purpose of this study was to develop a novel inverse PCR method capable of typing A. baumannii strains. The method involves three major steps: cutting of genomic DNA with a restriction enzyme, ligation, and PCR. In the first step, bacterial genomic DNA was digested with DpnI. In the second step, the digested genomic DNAs were ligated to form intramolecular circular DNAs. In the last step, the ligated circular DNAs were amplified by PCR with primers specific for ISAba1 and the amplified PCR products were electrophoresed. Twenty-two clinical isolates of A. baumannii were used for the evaluation of the inverse PCR (iPCR) typing method. Dendrogram analysis revealed two major clusters, similar to pulsed-field gel electrophoresis (PFGE) results. Three ISAba1-associated genes — bla_ampC, bla_OXA-66-like, and csuD — were amplified and detected in the clinical isolates. This novel iPCR typing method is comparable to PFGE in its ability to discriminate A. baumannii strains, and is a promising molecular epidemiological tool for investigating A. baumannii carrying ISAba1.     

Identification of Two Multidrug-Resistant <Emphasis Type="Italic">Pseudomonas aeruginosa</Emphasis> Clonal Lineages with a Countrywide Distribution in Hungary

The aim of this study was to identify class 1 integrons from extended-spectrum and metallo-β-lactamase-negative, multidrug-resistant Pseudomonas aeruginosa clinical isolates from Hungary and to characterize the isolates by phenotypic and molecular methods. Fourteen selected P. aeruginosa isolates resistant to ceftazidime, gentamicin, and ciprofloxacin were subjected to serotyping, random amplification of polymorphic DNA (RAPD), integron content analysis, and a phenotypic test to detect high-level production of AmpC. Four representative isolates were further analyzed by multilocus sequence typing. Two P. aeruginosa multidrug-resistant clonal lineages were identified with a countrywide distribution. The first lineage is characterized by serotype O4, RAPD genotype A, sequence type ST175, and the presence of a class 1 integron harbouring aadB and aadA13 gene cassettes in its variable region. The second lineage is characterized by serotype O6, RAPD genotype B, sequence type ST395, and a class 1 integron carrying a single aadB cassette. The corresponding isolates were recovered from altogether 11 towns in Hungary. ST175 and ST395 are the presently calculated founders of two distinct P. aeruginosa clonal complexes that appear to have a wide geographical distribution also outside Hungary. The multidrug-resistant phenotype associated with these two clonal lineages might have contributed to an increase in their frequency and to their subsequent diversification. Both P. aeruginosa lineages displayed ≥8-fold synergy with boronic acid/ceftazidime combinations, suggesting an AmpC-mediated resistance to ceftazidime. Our observations underscore the role of class 1 integrons in the spread of aminoglycoside resistance by clonal dissemination among P. aeruginosa clinical isolates in Hungary.     

Antimicrobial resistance and presence of <Emphasis Type="Italic">ileS-2</Emphasis> gene encoding mupirocin resistance in clinical isolates of methicillin-resistant <Emphasis Type="Italic">Staphylococcus</Emphasis> sp.

Seventy-eight staphylococcal strains were isolated from surgical-site, blood-stream and other hospital-acquired infections. Eighteen isolates were determined as methicillin (MET)-resistant S. aureus (MRSA), while the remaining were MET-resistant coagulase-negative staphylococci (CoNS). Fifty percent of CoNS strains were multiresistant, while 10 % of isolates were resistant only to β-lactams. Clinical isolates of CoNS were generally more resistant to antimicrobial agents than S. aureus strains. Thirty-nine % of S. aureus strains were resistant only to β-lactams. None of the MRSA strains carried ileS-2 gene; this gene was found in two strains of S. epidermidis.     

Biochemical and molecular characterization of <Emphasis Type="Italic">Cronobacter</Emphasis> spp<Emphasis Type="Italic">.</Emphasis> (formerly <Emphasis Type="Italic">Enterobacter sakazakii</Emphasis>) isolated from foods

The aim of this study was to identify and characterize Cronobacter spp. isolated from a range of foods. A total of 71 Cronobacter strains were isolated from 602 foods in our laboratory. The highest contamination was observed in foods of plant origin, e.g. spices, teas, chocolate, nuts, pastries and vegetables. On the basis of genus and species identification performed using genus-specific PCR, 16S rRNA sequencing and AFLP genotyping, most of the strains belonged to Cronobacter sakazakii. Biochemical profiling by the tests included in API 20E, complemented with relevant additional tests, classified the strains into 13 biogroups. AFLP genotyping facilitated discrimination of six main groups at the 70% similarity level and strain grouping correlated clearly with species identification. Our results indicate that molecular typing by AFLP may be applied as a useful tool not only for direct comparison of Cronobacter isolates, providing traceability, but also for the reliable species classification. Moreover, tracing of these bacteria in a wider variety of foods should be important to enhance the knowledge of their transmission.     

<Emphasis Type="Italic">Sporidiobolus johnsonii</Emphasis> and <Emphasis Type="Italic">Sporidiobolus salmonicolor</Emphasis> revisited

The relationship between Sporidiobolus johnsonii and S. salmonicolor was investigated using rDNA sequence data. Two statistically well-supported clades were obtained. One clade included the type strain of S. johnsonii and the other included the type strain of S. salmonicolor. However, some mating strains of S. salmonicolor were found in the S. johnsonii group. These strains belonged to mating type A2 and were sexually compatible with mating type A1 strains from the S. salmonicolor group. DNA–DNA reassociation values were high within each clade and moderate between the two clades. In the re-investigation of teliospore germination, we observed that the basidia of S. salmonicolor were two-celled. In S. johnsonii, basidia were not formed and teliospore germination resulted in direct formation of yeast cells. We hypothesize that the S. johnsonii clade is becoming genetically isolated from the S. salmonicolor group and that a speciation process is presently going on. We suspect that the observed sexual compatibility between strains of the S. johnsonii and S. salmonicolor groups and the possible genetic flow between the two species has little biological relevance because distinct phenotypes have been fixed in the two taxa and intermediate (hybrid) sequences for LSU and ITS rDNAs have not been detected. An erratum to this article can be found at     

Novel <Emphasis Type="Italic">Collophorina</Emphasis> and <Emphasis Type="Italic">Coniochaeta</Emphasis> species from <Emphasis Type="Italic">Euphorbia polycaulis</Emphasis>, an endemic plant in Iran

During a study on the biodiversity of yeasts and yeast-like ascomycetes from wild plants in Iran, four strains of yeast-like filamentous fungi were isolated from a healthy plant of Euphorbia polycaulis in the Qom Province, Iran (IR. of). All four strains formed small hyaline one-celled conidia from integrated conidiogenous cells directly on hyphae and sometimes on discrete phialides, as well as by microcyclic conidiation. Two strains additionally produced conidia in conidiomata that open by rupture. The internal transcribed spacer (ITS) sequences suggested the placement of these strains in the genera Collophorina (Leotiomycetes) and Coniochaeta (Sordariomycetes), respectively. Blast search results on NCBI GenBank and phylogenetic analyses of ITS, the glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and the translation elongation factor 1α (EF-1α) sequences, and the nuclear large subunit ribosomal gene (LSU), partial actin (ACT), and β-tubulin (TUB) sequences, respectively, revealed the isolates to belong to three new species, that are described here as Collophorina euphorbiae, Coniochaeta iranica, and C. euphorbiae. All three species are characterised by morphological, physiological, and molecular data.     

<Emphasis Type="Italic">Rhizobium</Emphasis> strains in the biological control of the phytopathogenic fungi <Emphasis Type="Italic">Sclerotium</Emphasis> (<Emphasis Type="Italic">Athelia</Emphasis>) <Emphasis Type="Italic">rolfsii</Emphasis> on the common bean

Aims

To identify Rhizobium strains’ ability to biocontrol Sclerotium rolfsii, a fungus that causes serious damage to the common bean and other important crops, 78 previously isolated rhizobia from common bean were assessed.

Methods

Dual cultures, volatiles, indole-acetic acid (IAA), siderophore production and 16S rRNA sequencing were employed to select strains for pot and field experiments.

Results

Thirty-three antagonistic strains were detected in dual cultures, 16 of which were able to inhibit ≥84% fungus mycelial growth. Antagonistic strains produced up to 36.5 μg mL^?1 of IAA, and a direct correlation was verified between IAA production and mycelium inhibition. SEMIA 460 inhibited 45% of mycelial growth through volatile compounds. 16S rRNA sequences confirmed strains as Rhizobium species. In pot condition, common bean plants grown on S. rolfsii-infested soil and inoculated with SEMIA 4032, 4077, 4088, 4080, 4085, or 439 presented less or no disease symptoms. The most efficient strains under field conditions, SEMIA 439 and 4088, decreased disease incidence by 18.3 and 14.5% of the S. rolfsii-infested control.

Conclusions

Rhizobium strains could be strong antagonists towards S. rolfsii growth. SEMIA 4032, 4077, 4088, 4080, 4085, and 439 are effective in the biological control of the collar rot of the common bean.

     

Common genomic features of <Emphasis Type="Italic">Campylobacter jejuni</Emphasis> subsp. <Emphasis Type="Italic">doylei</Emphasis> strains distinguish them from <Emphasis Type="Italic">C. jejuni</Emphasis> subsp. <Emphasis Type="Italic">jejuni</Emphasis>

Background  

Campylobacter jejuni has been divided into two subspecies: C. jejuni subsp. jejuni (Cjj) and C. jejuni subsp. doylei (Cjd). Nearly all of the C. jejuni strains isolated are Cjj; nevertheless, although Cjd strains are isolated infrequently, they differ from Cjj in two key aspects: they are obtained primarily from human clinical samples and are associated often with bacteremia, in addition to gastroenteritis. In this study, we utilized multilocus sequence typing (MLST) and a DNA microarray-based comparative genomic indexing (CGI) approach to examine the genomic diversity and gene content of Cjd strains.     

Adaptive mutation related to cellulose producibility in <Emphasis Type="Italic">Komagataeibacter medellinensis</Emphasis> (<Emphasis Type="Italic">Gluconacetobacter xylinus</Emphasis>) NBRC 3288

Gluconacetobacter xylinus (formerly Acetobacter xylinum and presently Komagataeibacter medellinensis) is known to produce cellulose as a stable pellicle. However, it is also well known to lose this ability very easily. We investigated the on and off mechanisms of cellulose producibility in two independent cellulose-producing strains, R1 and R2. Both these strains were isolated through a repetitive static culture of a non-cellulose-producing K. medellinensis NBRC 3288 parental strain. Two cellulose synthase operons, types I and II, of this strain are truncated by the frameshift mutation in the bcsBI gene and transposon insertion in the bcsCII gene, respectively. The draft genome sequencing of R1 and R2 strains revealed that in both strains the bcsBI gene was restored by deletion of a nucleotide in its C-rich region. This result suggests that the mutations in the bcsBI gene are responsible for the on and off mechanism of cellulose producibility. When we looked at the genomic DNA sequences of other Komagataeibacter species, several non-cellulose-producing strains were found to contain similar defects in the type I and/or type II cellulose synthase operons. Furthermore, the phylogenetic relationship among cellulose synthase genes conserved in other bacterial species was analyzed. We observed that the cellulose genes in the Komagataeibacter shared sequence similarities with the γ-proteobacterial species but not with the α-proteobacteria and that the type I and type II operons could be diverged from a same ancestor in Komagataeibacter.     

Screening and molecular identification of lactic acid bacteria from <Emphasis Type="Italic">gari</Emphasis> and <Emphasis Type="Italic">fufu</Emphasis> and <Emphasis Type="Italic">gari</Emphasis> effluents

Bacterial strains were isolated from cassava-derived food products and, for the first time, from cassava by-products, with a focus on gari, a flour-like product, and the effluents from the production processes for gari and fufu (a dough also made from cassava flour). A total of 47 strains were isolated, all of which were tested to determine their resistance to acidic pH and to bile salt environments. Four of the 47 isolates tested positive in both environments, and these four isolates also showed antibacterial behaviour towards both Gram-positive and Gram-negative microbial pathogens (i.e. Methicillin-resistance Staphylococcus aureus, Listeria monocytogenes, Bacillus cereus, Salmonella enteritidis, Escherichia coli, Escherichia coli (O157), Yersinia enterocolitica). In most cases, the antibacterial activity was related to bacteriocin production. Molecular identification analysis (16S rDNA and randomly amplified polymorphic DNA-PCR) revealed that the four isolates were different strains of the same species, Lactobacillus fermentum. These results demonstrate that bacteria isolated from cassava-derived food items and cassava by-products have interesting properties and could potentially be used as probiotics.     

Composition,structure, and biological properties of lipopolysaccharides from different strains of <Emphasis Type="Italic">Pseudomonas syringae</Emphasis> pv. <Emphasis Type="Italic">atrofaciens</Emphasis>

The composition, structure, and certain biological properties of lipopolysaccharides (LPS) isolated from six strains of bacteria Pseudomonas syringae pv. atrofaciens pathogenic for grain-crops (wheat, rye) are presented. The LPS-protein complexes were isolated by a sparing procedure (extraction from microbial cells with a weak salt solution). They reacted with the homologous O sera and contained one to three antigenic determinants. Against the cells of warm-blooded animals (mice, humans) they exhibited the biological activity typical of endotoxins (stimulation of cytokine production, mitogenetic activity, etc.). The LCD of the biovar type strain was highly toxic to mice sensitized with D-galactosamine. The structural components of LPS macromolecules obtained by mild acidic degradation were characterized: lipid A, core oligosaccharide, and O-specific polysaccharide (OPS). Fatty acids 3-HO-C_10:0, C_12:0, 2-HO-C_12:0, 3-HO-C_12:0, C_16:0, C_16:1, C_18:0, and C_18:1 were identified in lipid A of all the strains, as well as the components of the hydrophilic part: glucosamine (GlcN), ethanolamine (EtN), phosphate, and phosphoethanolamine (EtN-P). In the core LPS, glucose (Glc), rhamnose (Rha), L-glycero-D-manno-heptose (Hep), GlcN, galactosamine (GalN), 2-keto-3-deoxy-D-mannooctonoic acid (KDO), alanine (Ala), and phosphate were present. The O chain of all the strains consisted of repeated elements containing a linear chain of three to four L-(two strains) or D-Rha (four strains) residues supplemented with a single residue of 3-acetamido-3,6-dideoxy-D-galactose (D-Fucp3Nac), N-acetyl-D-glucosamine (D-GlcpNAc), D-fucose (D-Fucf), or D-Rhap (strain-dependent) as a side substituent. In different strains the substitution position for Rha residues in the repeated components of the major rhamnan chain was also different. One strain exhibited a unique type of O-chain heterogeneity. Immunochemical investigation of the LPS antigenic properties revealed the absence of close serological relations between the strains of one pathovar; this finding correlates with the differences in their OPS structure. Resemblance between the investigated strains and other P. syringae strains with similar LPS structures was revealed. The results of LPS analysis indicate the absence of correlation between the OPS structure and the pathovar affiliation of the strains.     

The antimicrobial potential of a new derivative of cathelicidin from <Emphasis Type="Italic">Bungarus fasciatus</Emphasis> against methicillin-resistant <Emphasis Type="Italic">Staphylococcus aureus</Emphasis>

Cathelicidins are a family of antimicrobial peptides which exhibit broad antimicrobial activities against antibiotic-resistant bacteria. Considering the progressive antibiotic resistance, cathelicidin is a candidate for use as an alternative approach to treat and overcome the challenge of antimicrobial resistance. Cathelicidin-BF (Cath-BF) is a short antimicrobial peptide, which was originally extracted from the venom of Bungarus fasciatus. Recent studies have reported that Cath-BF and some related derivatives exert strong antimicrobial and weak hemolytic properties. This study investigates the bactericidal and cytotoxic effects of Cath-BF and its analogs (Cath-A and Cath-B). Cath-A and Cath-B were designed to increase their net positive charge, to have more activity against methicillin resistant S. aureus (MRSA). The results of this study show that Cath-A, with a +17-net charge, has the most noteworthy antimicrobial activity against MRSA strains, with minimum inhibitory concentration (MIC) ranging between 32–128 μg/ml. The bacterial kinetic analysis by 1 × MIC concentration of each peptide shows that Cath-A neutralizes the clinical MRSA isolate for 60 min. The present data support the notion that increasing the positive net charge of antimicrobial peptides can increase their potential antimicrobial activity. Cath-A also displayed the weakest cytotoxicity effect against human umbilical vein endothelial and H9c2 rat cardiomyoblast cell lines. Analysis of the hemolytic activity reveals that all three peptides exhibit minor hemolytic activity against human erythrocytes at concentrations up to 250 μg/ml. Altogether, these results suggest that Cath-A and Cath-B are competent candidates as novel antimicrobial compounds against MRSA and possibly other multidrug resistant bacteria.     

The diversity of rhizobia nodulating the <Emphasis Type="Italic">Medicago</Emphasis>, <Emphasis Type="Italic">Melilotus</Emphasis> and <Emphasis Type="Italic">Trigonella</Emphasis> inoculation group in Egypt is marked by the dominance of two genetic types

Twenty four rhizobial strains were isolated from root nodules of Melilotus, Medicago and Trigonella plants growing wild in soils throughout Egypt. The nearly complete 16S rRNA gene sequence from each strain showed that 12 strains (50 %) were closely related to the Ensifer meliloti LMG6133^T type strain with identity values higher than 99.0 %, that 9 (37.5 %) strains were more than 99 % identical to the E. medicae WSM419^T type strain, and that 3 (12.5 %) strains showed 100 % identity with the type strain of N. huautlense S02^T. Accordingly, the diversity of rhizobial strains nodulating wild Melilotus, Medicago and Trigonella species in Egypt is marked by predominance of two genetic types, E. meliloti and E. medicae, although the frequency of isolation was slightly higher in E. meliloti. Sequencing of the symbiotic nodC gene from selected Medicago and Melilotus strains revealed that they were all similar to those of the E. meliloti LMG6133^T and E. medicae WSM419^T type strains, respectively. Similarly, nodC sequences of strains identified as members of the genus Neorhizobium were more than 99 % identical to that of N. galegae symbiovar officinalis HAMBI 114.     

Revision of the <Emphasis Type="Italic">Serrulati</Emphasis> species of <Emphasis Type="Italic">Penstemon</Emphasis> section <Emphasis Type="Italic">Saccanthera</Emphasis> subsection <Emphasis Type="Italic">Serrulati</Emphasis>

A revision of Penstemon sect. Saccanthera subsect. Serrulati includes a new species (P. salmonensis), a new variety (P. triphyllus var. infernalis), and the elevation of a subspecies to species (P. curtiflorus), bringing the total number of species to eight, which are keyed and described, complete with nomenclature and type citations.     

Genomewide analysis of <Emphasis Type="Italic">ABCB</Emphasis>s with a focus on <Emphasis Type="Italic">ABCB1</Emphasis> and <Emphasis Type="Italic">ABCB19</Emphasis> in <Emphasis Type="Italic">Malus domestica</Emphasis>

The B subfamily of ATP-binding cassette (ABC) proteins (ABCB) plays a vital role in auxin efflux. However, no systematic study has been done in apple. In this study, we performed genomewide identification and expression analyses of the ABCB family in Malus domestica for the first time. We identified a total of 25 apple ABCBs that were divided into three clusters based on the phylogenetic analysis. Most ABCBs within the same cluster demonstrated a similar exon–intron organization. Additionally, the digital expression profiles of ABCB genes shed light on their functional divergence. ABCB1 and ABCB19 are two well-studied auxin efflux carrier genes, and we found that their expression levels are higher in young shoots of M106 than in young shoots of M9. Since young shoots are the main source of auxin synthesis and auxin efflux involves in tree height control. This suggests that ABCB1 and ABCB19 may also take a part in the auxin efflux and tree height control in apple.