16S rDNA Analysis Research Articles

Peach witches’-broom, an emerging disease associated with ‘Candidatus Phytoplasma phoenicium’ and ‘Candidatus Phytoplasma aurantifolia’ in Iran

During field surveys carried out from 2013 to 2017 in the eight main peach producing provinces of Iran, symptoms of a phytoplasma-like peach witches'-broom disease (PWIB), inducing severe yellowing, little leaf, internode shortening, crown and stem witches’-broom, decline, and death, were observed. The aim of this work was to identify and characterize the agent(s) associated with PWIB by biological assays and molecular analyses. PWIB agents were successfully transmitted under controlled conditions from scions of in field-affected peach trees, exhibiting severe or mild symptoms, to peach and bitter almond seedlings inducing phytoplasma-like symptoms. A 16S rDNA fragment of 1250 bp was amplified by nested-PCR from all PWIB-affected trees and grafted seedlings. Nucleotide sequence identity, presence of species-specific signature sequences, in silico RFLP, single nucleotide polymorphisms, and phylogenetic analyses of 16S rDNA allowed the assignation of the phytoplasma strains identified in seven Iranian provinces in peach trees with severe PWIB symptoms to four SNP genetic lineages of ‘Ca. P. phoenicium’ (subgroup 16SrIX-B and its variant). PWIB phytoplasma strains identified in Abarkooh (Yazd province) in peach trees with mild symptoms were attributed to the species ‘Ca. P. aurantifolia’ (subgroup 16SrII-C). This report of a wide spread of ‘Ca. P. phoenicium’ in association with PWIB in Iran supported its capability of adaptation to a broad range of fruit tree species, such as peach, nectarine, and apricot. As ‘Ca. P. phoenicium’ and ‘Ca. P. aurantifolia’ are the etiological agents of other important plant diseases in Iran and neighbouring countries, further investigations are needed to determine the role played by peach in their epidemiological pathways.

Biocontrol and plant growth-promoting ability of plant-associated bacteria from tomato (Lycopersicum esculentum) under field condition

Forty-five bacterial isolates recovered from surface-sterilized root, stem and leaf tissues of tomato were studied for their antifungal activity against phytopathogens, and plant growth-promoting (PGP) and biocontrol traits. Six plant-associated bacteria suppressed all the pathogens tested under in vitro plate assay and also shown PGP and biocontrol traits. The six isolates showing PGP and biocontrol properties were identified as Bacillus spp., based on the microbial identification system (Biolog) and partial sequence analysis of 16S rDNA. Two independent field trials were conducted with biocontrol bacteria along with chemical control (Thiram+Fytolan) and control (Without treatment). The averaged results of two field trails revealed that tomato plants inoculated with BETS11 (11.73 t/ha) and BETR11 (11.24 t/ha) strains showed significantly higher yield and disease reduction on par with chemical control (11.81 t/ha). However, there was an increase in the yield with respect to uninoculated control except the isolate BETS5 (9.09 t/ha). Therefore, the isolates BETS11 and BETR11 may be used as efficient biofertilizer and bio-control agent for tomato production in the Island agricultural ecosystem.

Are habitat changes driving protist community shifts? A case study in Daya Bay, China

Protists play an important role in regulating marine ecosystems, and their diversity and community structure differ both temporally and spatially. Little research has been conducted on the structure and function of protists associated with coral reefs and artificial reefs, which are important and unique habitats for marine life. In this study, based on Illumina sequencing analysis of 18S rDNA, the diversity and community structure of protists in coral reef, artificial reef and open-water areas in Daya Bay were described for the first time. The biodiversity of protists in open-water areas was higher than that in artificial reefs and slightly higher than that in coral reefs, but there were no significant differences in protist alpha diversity among the different habitats or depths in Daya Bay. The depth of Daya Bay was not sufficient to significantly affect the distribution of the protist communities, while pH and salinity had the strongest impacts. Furthermore, the correlations between protist abundance and environmental variables of the water mass were much weaker than those between habitat and protist abundance. PERMANOVA revealed significant differences in protist diversity among the habitats. The interactions of living organisms and differences among habitats play key roles in the formation of protist communities, and artificial reefs were found to change the community structure of protists, suggesting that artificial reefs play a role similar to that of coral reefs to improve ecological functions and restore ecosystems.

Application of 18S rDNA Clone Library to Detect Diatom Population Diversity in Dianchi.

Objective To detect the diatom population diversity in Dianchi by constructing a 18S rDNA clone library. Methods DNA from diatoms in 6 water samples of Dianchi was amplified with diatom 18S rDNA specific primer.The 18S rDNA clone library was constructed, and clones were randomly selected for sequence. Sequence alignment was performed by BLAST. The diatom population distribution in Dianchi was analyzed and the phylogenetic tree of diatom 18S rDNA in Dianchi waters was established with the MEGA v7.0.14 software. Results Two hundred and forty clones were sequenced, with 167 diatom sequences obtained, including 11 diatom species such as Stephanodiscus, Diatoma, and Melosira. There were certain differences in diatom population distribution among the 6 samples. Conclusion The population distribution of diatom species in Dianchi shows unique features and the sequence analysis of diatom 18S rDNA has a certain reference value to the inference of forensic drowning sites.

Visualizing the effects of antibiotics on the mouse colonic mucus layer.

Objective:Mucus provides a protective barrier separating sensitive epithelial surfaces from the outside world. The mouse colonic mucus is organized as a bacteria-free inner layer and a bacteria-colonized outer layer. Antibiotic treatments are known to disturb gut microbiota, but their effect on the mucosal barrier is rarely discussed. The aim was to evaluate and visualize the impact of antibiotics on the colonic mucus and the microbial community.Materials and Methods:Two sets of experiments were conducted. In the antibiotic experiment, mice orally ingested both streptomycin and bacitracin for 7 days. In the recovery experiment, mice were allowed to recover for 7 days without antibiotics after having received the 7-day antibiotic treatment. Mouse colons were isolated and divided into proximal, middle, and distal parts. Specimens were examined under a transmission electron microscope to identify morphological changes. The gut microbial community was evaluated by analyzing 16S rDNA sequences isolated from the different parts of the mouse colon.Results:The antibiotic-treated mice were physiologically normal. However, a significantly increased inner mucus layer in the proximal and middle colon and a dramatic decrease in bacterial numbers in the outer mucus layers were observed. The 16S rDNA compositions showed a similarity in the dominant taxa among different colon sections. While control mice had a diverse microbiota, antibiotic treatments effectively eliminated most of the bacteria, such that the community was dominated by only one genus (Turicibacter or Staphylococcus). Furthermore, following antibiotic withdrawal in treated mice, the thickness of the inner mucus layer returned to control levels, and the microbial community regained a more complex structure, dominated by Firmicutes, Bacteroidetes, and Proteobacteria.Conclusions:Our results indicated that antibiotic treatments not only disturbed the microbiota but also altered the structure of the mucus layer. After the withdrawal of antibiotics, the mucus layer was quickly regenerated within days, probably in response to microbial growth. The recolonization by gut inhabitants with diverse ecological roles, such as mucin-degraders and fermenters indicate that the gut ecosystem is functionally sound and highly resilient.

Isolation and Identification of Pesticides Degrading Bacteria from Farmland Soil

Pesticides are recognized to be the threat to the environment and associated with a wide range of serious diseases including respiratory diseases, cancer and even birth defects. In this study, six-different bacterial strains capable of degrading Carbofuran, Emamectin Benzoate and Thiamethoxam were isolated from eight different soil samples. The isolates were characterized by using different conventional and molecular methods. The strains were identified molecularly into different genotypes using amplified ribosomal DNA restriction analysis (ARDRA) and partial sequencing of 16S rDNA. The ARDRA pattern clustered them into 3 groups. Among the isolates three were identified as Achromobacter spp. and one as Diaphorobacter sp. by biochemical tests. It was further confirmed by the partial 16S rDNA sequencing. The two identified potential bacteria can be used for biodegradation of different pesticides which can have a significant environmental impact in soil farm.
 Bangladesh J Microbiol, Volume 35 Number 2 December 2018, pp 90-94

Comparison of some Molecular Markers for Tick Species Identification

Ticks are obligate blood-sucking ectoparasites of vertebrates. Since many tick identification studies are based on the analysis of 16S rDNA, 12S rDNA and ITS-1, 2 rDNA genes, we aimed to compare the performance of these molecular markers of common use for the identification of ticks, under a diagnostic laboratory environment. Overall, 192 tick specimens were collected through the state of Texas from January 2014 to August 2015 and the species was determined by both morphology and molecular amplification using the 16S rDNA, 12S rDNA, ITS1 and ITS2. The species collected were identified by molecular techniques as Dermacentor albipictus, D. variabilis, Amblyomma americanum, Ixodes scapularis, A. cajennense, Rhipicephalus sanguineus and Carios capensis. ITS1 and ITS2 were not able to prove consistent amplification and therefore have been considered as potential markers for tick identification. The use of mitochondrial genes in tick identification showed to provide more consistent results in the diagnostic environment.

Sensitivity of Heterotrophic Bacteria in the Low-Salinity Water Areas and Estuary in Siak District toward Pathogenic Bacteria in Fish

The high rate of bacterial diseases in fishes and shrimps has lead scientists seek for natural antibiotic products that would act as a solution. An example of this product is the secondary metabolic products from heterotrophic bacteria. These bacteria could easily be found in many water regions and estuaries, including the Siak District, Riau, Indonesia. Therefore, this study aims at determining the ability of bacterial isolates in inhibiting the growth of pathogens (Vibrio alginolyticus, Aeromonas hydrophila, and Pseudomonas sp.). The research was conducted from June to September 2018. It actuates the type of heterotrophic bacteria in the sampling area using the PCR technique. The phylogenetic structure of bacterial isolates obtained during this study was assessed by nucleotide sequencing of the 16S rRNA gene. The antagonism test showed that bacteria had the ability to inhibit the growth of pathogens (Vibrio alginolyticus, Aeromonas hydrophila, and Pseudomonas sp.). The results showed that 25 pure bacterial isolates were obtained, in which 10 of those were carried out by DNA sequencing; hence, it could be used as antimicrobes. Based on the analysis of 16S rDNA, 10 isolates were identified: 6 were Bacillus cereus and 2 were Pseudomonas aeruginosa with homology levels ranging from 97 to 99%, while the remaining two were suspected as the new species of isolates. From the result, it could be concluded that heterotrophic bacteria are found to be better used as antipathogens against Vibrio alginolitycus than hydrophila and Pseudomonas sp.

Morphological and molecular characterization of Glossidium pedatum Looss, 1899 and Orientocreadium batrachoides Tubangui, 1931 from sharptooth catfish, Clarias gariepinus (Burchell, 1822)

The superfamily Plagiorchioidea has a considerable number of genera and species with great uncertainty of their phylogenetic position. The objectives of the current study were to specifically describe the morphology and determine for the first time the phylogenetic position of Glossidium pedatum and Orientocreadium batrachoides. Examination of G. pedatum using conventional light and scanning microscopy techniques revealed undescribed features related to the digestive system, the presence of papillae-like lateral lappets, and terminal lobes covered with backwardly directed spines. Orientocreadium batrachoides revealed a pharynx that is four lobed anteriorly. Both the large (28S) and small (18S) subunits of the ribosomal genome, analysed through Bayesian inference and maximum likelihood, were used to genetically characterise these species. Phylogenies indicate that G. pedatum does not fit well into any known family within the Plagiorchioidea, as currently indicated in various systematic structures based on morphology. However, G. pedatum was closely related to Haematoloechidae according to analyses of 18S and 28S rDNA. Based on 28S rDNA, O. batrachoides formed a well-supported clade with Orientocreadium pseudobagri within the family Orientocreadiidae. In turn, Orientocreadiidae is closely related to Leptophallidae. The current study provides essential information that could be helpful to assign the family for Glossidium in future studies. Characterisation of life-cycle stages may be necessary to fully elucidate the systematic position of G. pedatum.

Isolation and Characterization of Bacterium isolated from Bantala Tannery Solid Wastes

Leather industries that uses the conventional chrome tanning process are subjected to high risk of contamination due to the emission of toxic Cr(VI) that poses a serious threat to the environment and human’s wellbeing. The present study were made to isolate and characterize chromium tolerant bacteria in the samples collected from four different plots of Bantala Tannery, Kolkata, West Bengal, India. Pure chromium tolerant bacterial strains were isolated from the tannery sludge samples and their relative MIC (Minimum Inhibitory Concentration) were recorded at different concentrations of Cr (VI) salts to select the highest chromium tolerant bacterium. The selected bacterium was further taken for their growth studies followed by different cultural, morphological and molecular analysis (16S rDNA). The bacterial strain was further studied through SEM (Scanning Electron microscopy) and EDX (Energy Dispersive X-ray) spectroscopy which revealed that TW4 was a gram positive, rod shaped, endospore forming, pleomorphic bacterium with phylogenetic similarities with Isoptericola sp. and genebank accession number SUB1732465 TW4 KX640927.

Effects of salinity on the biological performance of anaerobic membrane bioreactor

The performance of anaerobic membrane bioreactor (AnMBR) was evaluated treating synthetic wastewater with various concentrations of NaCl (0–40 g/L), as well as the recovery phase. The effluent COD removal efficiency decreased from 96.4% to 95.0%, 91.4%, 86.7% and 77.7% with stepwise increasing of salt concentration from 0 to 5, 10, 20 and 40 g NaCl/L, respectively, then gradually increased to 94.1% during the recovery phase. Additionally, the significant changes in the content and composition of soluble microbial products (SMP) and extracellular polymer substance (EPS) were obtained under higher salt stress. GC-MS analyses were carried out for the effluent, and some new types of compounds, such as Dodecane, Undecane, and Ethyl Acetate, were found during salt exposure phases. The characterization of the microbial community was also investigated based on the analysis of genomic 16S rDNA, revealing the increasing salinity (5–40 g NaCl/L) could reduce the diversity of sludge microbial community in AnMBR. Meanwhile, the significant effects on the composition of dominate phyla (Proteobacteria, Bacteroidetes, Firmicutes and Chloroflexi) were found during the salt exposure phase.

Nitrogen removal and responses of bacterial communities in activated sludge under different operational manipulations.

Operational conditions are often manipulated to improve the nitrogen removal performance of wastewater treatment, yet the impacts of operational conditions on microbial communities were still not well understood. There is a pressing need to understand the microbial mechanisms that link operation manipulation and nitrogen removal performance. In this study, high-throughput analysis of 16S rDNA and quantitative polymerase chain reaction of functional genes were used to identify the microbial response to operational manipulations. The results showed that alteration of operational parameters could change the bacterial communities at the genera level and denitrification guild gradually dominated in the activated sludge bacterial communities. Heterotrophic Hyphomicrobium and Chromatiaceae drove the kinetic of dominant genera and denitrification guild. Carbon source supplement was the most efficient strategy for improving nitrogen removal, and greatly increased the abundance of denitrifiers and denitrification genes. However, carbon source supplement inhibited expression activities of denitrification genes, as well as the proliferation of autotrophic denitrifiers, and it was supposed to be unfavorable in terms of cost over the long term. The result should bring new inspiration for improving the effect of WWTP performance through the manipulation of operational parameters.

Analysis of nematode-endosymbiont coevolution in the Xiphinema americanum species complex using molecular markers of variable evolutionary rates

Summary Bacterial symbioses play important roles in shaping diverse biological processes in nematodes, and serve as targets in nematode biocontrol strategies. Focusing on the Xiphinema americanum species complex, we expanded upon recent research investigating patterns of coevolution between Xiphinema spp. and Xiphinematobacter spp., utilising two symbiont genetic markers of varying evolutionary rates. Phylogenetic analysis of nematode mitochondrial DNA (mtDNA) revealed five strongly supported major clades. Analysis of slow-evolving 16S rDNA in bacterial symbionts resulted in a phylogenetic topology composed of four major clades that grouped taxa highly congruent with the nematode mtDNA topology. A faster evolving protein-coding symbiont gene (nad) provided more phylogenetic resolution with seven well-supported clades, also congruent with the nematode mtDNA tree topology. Our results reinforce recent studies suggesting extensive coevolution between Xiphinema spp. and their vertically transmitted endosymbionts Xiphinematobacter spp. and illustrate the advantages of including genetic markers of varying evolutionary rates in coevolutionary and phylogenetic studies.

Screening and enzymatic activity of high-efficiency gellan lyase producing bacteria Pseudoalteromonas hodoensis PE1

ABSTRACT Gellan is a widely used microbial polysaccharide and one of the more effective ways to expand its application value would be to investigate the mechanism of gellan lyase and to produce gellan oligosaccharide. In this study, efficient gellan degrading bacteria were screened. One of the strains with high efficient gellan degradation capacity was labeled PE1. Through physiological and biochemical analysis of 16S rDNA, the species was identified as Pseudoalteromonas hodoensis. The optimum conditions for enzymatic activity and how it was affected by metal ions were determined, and the results showed that the lyase activities were much higher than those of previously reported (about 20 times). The gellan degradation products were determined by thin-layer chromatography and the oligosaccharides were determined by high-efficiency liquid chromatography to analyze the action site of lyase. This study laid a solid foundation which elucidates the production and application of gellan oligosaccharides. Research highlights ● High efficiency gellan lyase producing bacteria ● Optimization of reaction conditions for gellan degradation ● Oligosaccharides were detected by TLC and HPLC to speculate the lyase action sites.

Identification of Petroleum Degrading Bacteria and Construction of Petroleum Degrading Agent

The aim of this study is to construct petroleum degrading agent (PDA) which can effectively degrade oil. By enrichment, domestication, and separation of culture from the soil sample of Qianjiang Guanghua Oilfield, the pure culture of three petroleum degrading bacteria G-40, G-53, and G-94 was identified from the medium supplemented with oil, which served as the sole source of carbon. The species of G-40 and G-53 were preliminarily identified and classified by morphological observation, physiological and biochemical determination, and sequence analyses of 16S rDNA. The species of G-94 was preliminarily identified and classified by morphological observation, physiological and biochemical determination, and sequence analyses of ITS rDNA. The optimal inoculation proportion of these three bacteria strains and bran proportion in composition of PDA were determined through orthogonal test. G-40, G-53, and G-94 were isolated and identified as Brevibacillus laterosporus, Tsukamurella inchonensis, and Candida tropicalis, respectively. To construct petroleum degrading agent, the optimum inoculation proportion of the three bacteria strains was A1B3C3 (G-40:G-53:G-94 = 1:4:4); and the optimum proportion of bran was D1E1F2 (soybean meal:corn flour:bran = 1:1:2). The oil removal rate of the constructed petroleum degrading agent reached to 42.32% on day 10 under the optimal proportion of bacteria inoculation and bran composition. Petroleum degrading bacteria can effectively degrade petroleum for its own growth. This study identified three petroleum degrading bacteria strains and proposed a petroleum degrading agent by studying the optimal inoculation proportion of the three bacterial strains and the accompanying bran. Our research could provide potential microbial resources for bioremediation of petroleum-contaminated soil.

Detection and characterization of an emerging type of Babesia sp. similar to Babesia motasi for the first case of human babesiosis and ticks in Korea

ABSTRACT Babesiosis is a tick-transmitted intraerythrocytic zoonosis. In Korea, the first mortalities were reported in 2005 due to Babesia sp. detection in sheep; herein we report epidemiological and genetic characteristics of a second case of babesiosis. Microscopic analysis of patient blood revealed polymorphic merozoites. To detect Babesia spp., PCR was performed using Babesia specific primers for β-tubulin, 18S rDNA, COB, and COX3 gene fragments. 18S rDNA analysis for Babesia sp., showed 98% homology with ovine Babesia sp. and with Babesia infections in Korea in 2005. Moreover, phylogenetic analysis of 18S rDNA, COB, and COX3 revealed close associations with B. motasi. For identifying the infectious agent, Haemaphysalis longicornis (296) and Haemaphysalis flava (301) were collected around the previous residence of the babesiosis patient. Babesia genes were identified in three H. longicornis: one sample was identified as B. microti and two samples were 98% homologous to B. motasi. Our study is the first direct confirmation of the infectious agent for human babesiosis. This case most likely resulted from tick bites from ticks near the patient house of the babesiosis patient. H. longicornis has been implicated as a vector of B. microti and other Babesia sp. infections.

Watanabea acidotolerans: A new trebouxiophyte lineage (Chlorophyta) inhabiting low pH environments from Europe to South America

SUMMARYHere we studied a new Watanabea strain CAUP H 8901‐CRYO isolated from an extremely acidic (pH 2.6) pit lake in Czechia. We used morphological, ultrastructural and molecular data to ascertain its taxonomic position and phylogenetic relationships within the genus Watanabea. The morphology of the studied strain matched the formal Watanabea description, including its most characteristic feature, the production of two types of autospores. The new isolate morphologically and ultrastructurally resembled the Watanabea type species, W. reniformis. However, it differed from W. borysthenica by having a pyrenoid not surrounded by starch grains. Molecular phylogenetic analyses of nuclear 18S rDNA and plastid rbcL showed that the strain CAUP H 8901‐CRYO formed an independent lineage within the genus Watanabea. Furthermore, analyses of nuclear ITS2 secondary structure demonstrated an additional side loop coiling from the helix III, the unique feature of CAUP H 8901‐CRYO, not present in the authentic strain of W. reniformis SAG 211‐9b. The ITS2 secondary structures of the two strains also differed by one compensatory base change (CBC) and a number of additional nucleotide substitutions. The new acidotolerant strain and another Watanabea isolate from a naturally acidic lake in Argentina were identical in their plastid rbcL sequence. Consequently, here we proposed a new species, Watanabea acidotolerans, to accommodate a lineage of microalgae with a possible worldwide distribution and tolerance to low pH habitats.

Versuriga anadyomene, a newly recorded scyphozoan jellyfish (Scyphozoa: Rhizostomae) in Chinese waters

Scyphozoans are currently causing great concern worldwide due to the effects of their blooms on the marine environment. During a field survey in Beibu Gulf, South China Sea, on 27 May 2015, we found specimens of a rhizostome jellyfish that had not previously been recorded in Chinese seas. The morphological characters and DNA sequences of several specimens were examined in the laboratory. These specimens had the following morphological characters: hemispherical umbrella with reticular grooves; eight large semicircular velar lappets alternating with narrow lappets in each of the 8 octants; laterally flattened mouth-arms with numerous flat, membranous branches bearing many clubs and intermediate filaments; non-anastomosed broad perradial canals and anastomosed narrow interradial canals. The morphological characters of these rhizostome jellyfish were consistent with descriptions of Versuriga anadyomene. Furthermore, phylogenetic analysis of mitochondrial 16S rDNA and nuclear 18S rDNA gene fragments confirmed that these specimens were in the same cluster as V. anadyomene collected in Palau. Therefore, this rhizostome jellyfish was identified as V. anadyomene. This is the first record of the genus Versuriga and the species V. anadyomene in Chinese seas. The arrival of this species may be attributed to physical transport from the coastal waters of South East Asia.

Identification and antibiotic susceptibility of lactobacilli isolated from turkeys

BackgroundThe aim of this study was to identify Lactobacillus isolates derived from turkeys from six Polish farms and to characterize their phenotypic and genotypic antibiotic resistance profiles.ResultsAmong 62 isolates identified by MALDI-TOF mass spectrometry and restriction analysis of 16S rDNA, the dominant species was L. salivarius (35%), followed by L. crispatus (21%), L. ingluviei (14.5%) and L. johnsonii (10%). A high prevalence of resistance to tetracycline (68% resistant isolates), lincomycin (64.5%) and enrofloxacin (60%) among the lactobacilli tested was observed. Fewer than 50% isolates were resistant to ampicillin (47%), erythromycin (45%), streptomycin (31%), chloramphenicol (29%) and gentamicin (10%). As many as 64,5% of the isolates showed multidrug resistance. High MIC values for ampicillin (≥64 μg/ml) were usually accompanied by elevated MICs for cephalosporins (≥16 μg/ml) and high MICs for tiamulin, i.e. ≥32 μg/ml, were noted in most of the turkey lactobacilli (61%). The occurrence of resistance genes was associated with phenotypic resistance, with the exception of five phenotypically susceptible isolates that contained the tetM, tetL, ermC, ermB or cat genes. The most frequently identified were ermB (45% isolates), tetL (40%), tetW (37%) and tetM (29%), and the occurrence of lnuA (18%), cat (10%), ermC (6%), ant(6)-Ia (5%) and aadE (5%) was less frequent. The mechanism of ampicillin resistance has not been elucidated, but the results of nitrocefin test confirmed that it is not involved in the production of beta-lactamases.ConclusionsThe high rate of antibiotic resistance observed in this study indicates the need to implement the principles of rational use of antibiotics in poultry. The presence of transmissible resistant genes in lactobacilli may contribute to the development of antibiotic resistant pathogenic strains that pose a threat to both poultry and consumers. The results of these studies may be useful for committees providing guidance on antibiotic susceptibility of microorganisms in order to revise and supplement current microbiological cut-offs values within the genus Lactobacillus.

Bacterial leaf spot of lettuce caused by Xanthomonas hortorum pv. vitians in the Aegean Region of Turkey

Samples of diseased plants were collected from 12 lettuce fields in Aydin province of the Aegean Region of Turkey. A total of 8 bacterial isolates were identified by morphological characterization, sequence analysis of 16S rDNA and gyrB genes, and pathogenicity. The survey included twelve lettuce fields of three different cultivars [Yedikule (romaine type), Robinson and Chianti (iceberg type)]. The incidence of the disease ranged from 48 to 95%. Plants of cv. Chianti were the most severely infected cultivars. To our knowledge, this is the first report of the presence of Xanthomonas hortorum pv. vitians in lettuce plants in Turkey.