Antagonist activities and phylogenetic relationships of actinomycetes isolated from an Artemisia habitat.

Diverse habitats have been screened for novel antimicrobial actinomycetes, while others remain unexplored. In this study, we analyzed the bioactivities of actinomycetes cultured from rhizosphere soils of the desert plant Artemisia tridentata and the nearby bulk soils. Actinomycetes were screened for antifungal and antibacterial activities toward a panel of plant pathogens; all comparisons were between activities of rhizosphere soil isolates toward those of its counterpart bulk soil. A selected group of the strongest antifungal isolates were also tested against two antifungal-drug resistant strains of Candida albicans. 16S rDNA partial sequences and phylogenetic analysis of isolates that showed broad-spectrum antifungal activities were performed. Forty-two out of 200 and two soil isolated actinomycetes were selected for their strong antifungal activities. The highest proportion of isolates (p<0.05) from rhizosphere soil of an old plant showed antagonism against gram-positive bacteria (0.483 and 0.224 proportions against Bacillus subtilis and Rathayibacter tritici, respectively), and phytopathogenic fungi (0.259, 0.431, and 0.345 proportions against Fusarium oxysporum, Rhizoctonia solani and Pythium ultimum, respectively), while the highest antagonism against the gram-negative bacteria predominated in isolates from the bulk soils. Isolates from a rhizosphere soil of a young plant were characterized for strong antagonist activities against Fusarium oxysporum (0.333 proportion, p<0.05). Phylogenetic analysis of 16S rDNA sequences showed that isolates that exhibited strong antifungal activity were genetically similar. We conclude that the rhizosphere soil of A. tridentata is an excellent source for discovery of actinomycetes with potentially novel antifungal compounds.

Diversity of Endophytic Fungal Community in Leaves of Artemisia argyi Based on High-throughput Amplicon Sequencing.

To investigate the community structure and diversity of endophytic fungi in the leaves of Artemisia argyi, leaf samples were collected from five A. argyi varieties grown in different cultivation areas in China, namely, Tangyin Beiai in Henan (BA), Qichun Qiai in Hubei (QA), Wanai in Nanyang in Henan (WA), Haiai in Ningbo in Zhejiang (HA), and Anguo Qiai in Anguo in Hebei (AQA), and analyzed using Illumina high-throughput sequencing technology. A total of 365,919 pairs of reads were obtained, and the number of operational taxonomic units for each sample was between 165 and 285. The alpha diversity of the QA and BA samples was higher, and a total of two phyla, eight classes, 12 orders, 15 families, and 16 genera were detected. At the genus level, significant differences were noted in the dominant genera among the samples, with three genera being shared in all the samples. The dominant genus in QA was Erythrobasidium, while that in AQA, HA, and BA was Sporobolomyces, and that in WA was Alternaria, reaching a proportion of 16.50%. These results showed that the fungal community structure and diversity in QA and BA were high. The endophytes are of great importance to the plants, especially for protection, phytohormone and other phytochemical production, and nutrition. Therefore, this study may be significant with the industrial perspective of Artemisia species.

Pathological Impact on the Phyllosphere Microbiota of Artemisia argyi by Haze.

The pathological impact of haze upon the phyllosphere microbiota awaits investigation. A moderate degree of haze environment and a clean control were selected in Chengdu, China. Artemisia argyi, a ubiquitously distributed and extensively applied Chinese herb, was also chosen for experiment. Total genome DNA was extracted from leaf samples, and for metagenome sequencing, an Illumina HiSeq 2500 platform was applied. The results showed that the gene numbers of phyllosphere microbiota derived from haze leaves were lower than those of the clean control. The phyllosphere microbiota derived from both haze and clean groups shared the same top ten phyla; the abundances of Proteobacteria, Actinomycetes and Anorthococcuso of the haze group were substantially increased, while Ascomycetes and Basidiomycetes decreased. At the genus level, the abundances of Nocardia, Paracoccus, Marmoricola and Knoelia from haze leaves were markedly increased, while the yeasts were statistically decreased. KEGG retrieval demonstrated that the functional genes were most annotated to metabolism. An interesting find of this work is that the phyllosphere microbiota responsible for the synthesis of primary and secondary metabolites in A. argyi were significantly increased under a haze environment. Relatively enriched genes annotated by eggNOG belong to replication, recombination and repair, and genes classified into the glycoside hydrolase and glycosyltransferase enzymes were significantly increased. In summary, we found that both structure and function of phyllosphere microbiota are globally impacted by haze, while primary and secondary metabolites responsible for haze tolerance were considerably increased. These results suggest an adaptive strategy of plants for tolerating and confronting haze damage.

Polyketides and Terpenoids with Potent Antibacterial Activities from the Artemisia argyi-Derived Fungus Trichoderma koningiopsis QA-3.

The AcOEt extract of Artemisia argyi-derived fungus Trichoderma koningiopsis QA-3 showed potent inhibitory activity against pathogenic bacteria. Fractionation of the extract resulted in the isolation of three new polyketides (1-3) and two new terpenoids (4 and 5), together with three known metabolites (6-8). Their chemical structures were analyzed by NMR spectra, ECD, HR-ESI-MS or HR-EI-MS, optical rotation, and X-ray crystallographic data, as well as by comparison with literature reports. In the antibacterial assays, 3-hydroxyharziandione (4) showed potent activity against human pathogen Escherichia coli with an MIC value of 0.5 µg/mL, while 6-(3-hydroxypent-1-en-1-yl)-2H-pyran-2-one exhibited strong activity against marine-derived aquatic pathogen Micrococcus luteus with an MIC value of 1.0 µg/mL.

Bioactive seco-Sativene Sesquiterpenoids from an Artemisia desertorum Endophytic Fungus, Cochliobolus sativus.

A series of seco-sativene sesquiterpenoids (1-11) including two new natural products (2 and 3), four new analogues (4-7), and six known analogues, helminthosporic acid (1), drechslerine A (8), drechslerine B (9), helminthosporol (10), helminthosporal acid (11), and isosativenediol (12), were purified from the endophytic fungus Cochliobolus sativus isolated from a desert plant, Artemisia desertorum. The stereochemistry of helminthosporic acid (1) was established for the first time by X-ray diffraction, and the structures including relative and absolute configurations of these new compounds were determined by NMR and CD spectra together with biosynthetic considerations. Compounds 5-7 are the first seco-sativene sesquiterpenoids possessing a glucose group on C-15, C-15, and C-14, respectively. Compounds 1, 7, 9, and 11 displayed strong phytotoxic effects on corn leaves by producing visible lesions, and helminthosporic acid (1) was shown to promote division of leaves and roots of Arabidopsis thaliana with a dose-dependent relationship.

Characterization of biosurfactant produced by the endophyte Burkholderia sp. WYAT7 and evaluation of its antibacterial and antibiofilm potentials.

The endophyte Burkholderia sp. WYAT7 isolated from the medicinal plant Artemisia nilagirica (Clarke) Pamp. was analyzed for its ability to produce biosurfactant. The evaluation of biosurfactant production was conducted using different screening methods which confirmed the presence of biosurfactant in the culture supernatant. CTAB- methylene blue agar plate method was used for the screening of glycolipid biosurfactant production. The biosurfactant produced by the bacteria effectively metabolized hydrocarbons present in the bacterial culture media. Fourier transform infrared spectroscopic (FTIR) analysis of biosurfactant provided the details regarding OH stretching, stretching vibrations of acyl chain, CO stretching, stretching vibrations of ether and vibrations of glycosidic linkages in the biosurfactant. The stretching vibrations of glycosidic linkage in the fingerprint regions of FTIR spectrum (1200 cm-1 to 800 cm-1 regions) confirms that the biosurfactant produced was a glycolipid. The GC-MS analysis confirmed the methyl and ethyl esters of fatty acids. The biosurfactant from the bacteria exhibited antibacterial activity against bacterial pathogens such as Pseudomonas aeruginosa (MTCC 2453), Escherichia coli (MTCC 1610), Salmonella paratyphi and Bacillus subtilis. The glycolipid biosurfactant had antibiofilm activity as evidenced in Staphylococcus aureus (MTCC 1430). All these results indicated the beneficial effect of the biosurfactant in plant-endophyte interactions. The properties exhibited by the biosurfactant suggest that it can be exploited commercially for the production of novel antibiotics.

Trichocadinins B-G: Antimicrobial Cadinane Sesquiterpenes from Trichoderma virens QA-8, an Endophytic Fungus Obtained from the Medicinal Plant Artemisia argyi.

Trichocadinins B-G (1-6), six new cadinane-type sesquiterpene derivatives, each with C-14 carboxyl functionality, were isolated from the culture extract of Trichoderma virens QA-8, an endophytic fungus obtained from the fresh inner tissue of the medicinal plant Artemisia argyi. Their structures were elucidated by interpretation of the NMR spectroscopic and mass spectrometric data. The structures and absolute configurations of compounds 1 and 3 were confirmed by X-ray crystallographic analysis. Compounds 1-3 showed antibacterial and antifungal activity.

Bacterial endophytes from Artemisia nilagirica (Clarke) Pamp., with antibacterial efficacy against human pathogens.

A study was conducted to isolate and characterize endophytes from Artemisia nilagirica, a traditional medicinal plant. The plant was collected from Western Ghats, India. Endophytes isolated included Arthrobacter sp. WWAT1, Pseudomonas sp. WYAT2, Microbacterium sp. WYAT3, Psychrobacter sp. WBAT4, Enterobacter sp. WWAT5, Bacillus sp. WBAT6, Kosakonia cowanii WBAT7, Bacillus sp. WBAT8, Bacillus sp. WBAT9, Chromobacterium violaceum WVAT6, Serratia sp.WPAT8 and Burkholderia sp. WYAT7. Of these two bacteria, Chromobacterium violaceum strain WVAT6 and Burkholderia sp. strain WYAT exhibited antibacterial property against human pathogens. Similar to the environmental isolates, Burkholderia sp. WYAT7 showed pleomorphism and produced different enzymes, whereas like clinical strains they showed multidrug resistance, for their survival in different environmental conditions. Chromobacterium violaceum WVAT6 exhibited rod shape morphology and showed multiple drug resistance except to erythromycin, tetracycline and gentamicin antibiotics. Both produced biofilm and enzymes such as protease and lipase. The antimicrobial compounds from these endophytes may find application in the preparation of antimicrobial formulations.

Seed mucilage interacts with soil microbial community and physiochemical processes to affect seedling emergence on desert sand dunes.

Seedling emergence is a critical stage in the establishment of desert plants. Soil microbes participate in plant growth and development, but information is lacking with regard to the role of microbes on seedling emergence. We applied the biocides (captan and streptomycin) to assess how seed mucilage interacts with soil microbial community and physiochemical processes to affect seedling emergence of Artemisia sphaerocephala on the desert sand dune. Fungal and bacterial community composition and diversity and fungal-bacterial interactions were changed by both captan and streptomycin. Mucilage increased soil enzyme activities and fungal-bacterial interactions. Highest seedling emergence occurred under streptomycin and mucilage treatment. Members of the phyla Firmicutes and Glomeromycota were the keystone species that improved A. sphaerocephala seedling emergence, by increasing resistance of young seedlings to drought and pathogen. Seed mucilage directly improved seedling emergence and indirectly interacted with the soil microbial community through strengthening fungal-bacterial interactions and providing favourable environment for soil enzymes to affect seedling emergence. Our study provides a comprehensive understanding of the regulatory mechanisms by which soil microbial community and seed mucilage interactively promote successful establishment of populations of desert plants on the barren and stressful sand dune.

Artemisia pollen is the main vector for airborne endotoxin.

BACKGROUND: Endotoxin (LPS) released from gram-negative bacteria causes strong immunologic and inflammatory effects and, when airborne, can contribute to respiratory conditions, such as allergic asthma. OBJECTIVES: We sought to identify the source of airborne endotoxin and the effect of this endotoxin on allergic sensitization. METHODS: We determined LPS levels in outdoor air on a daily basis for 4 consecutive years in Munich (Germany) and Davos (Switzerland). Air was sampled as particulate matter (PM) greater than 10 µm (PM > 10) and PM between 2.5 and 10 µm. LPS levels were determined by using the recombinant Factor C assay. RESULTS: More than 60% of the annual endotoxin exposure was detected in the PM > 10 fraction, showing that bacteria do not aerosolize as independent units or aggregates but adhered to large particles. In Munich 70% of annual exposure was detected between June 12th and August 28th. Multivariate modeling showed that endotoxin levels could be explained by phenological parameters (ie, plant growth). Indeed, days with high airborne endotoxin levels correlated well with the amount of Artemisia pollen in the air. Pollen collected from plants across Europe (100 locations) showed that the highest levels of endotoxin were detected on Artemisia vulgaris (mugwort) pollen, with little on other pollen. Microbiome analysis showed that LPS concentrations on mugwort pollen were related to the presence of Pseudomonas species and Pantoea species communities. In a mouse model of allergic disease, the presence of LPS on mugwort pollen was needed for allergic sensitization. CONCLUSIONS: The majority of airborne endotoxin stems from bacteria dispersed with pollen of only one plant: mugwort. This LPS was essential for inducing inflammation of the lung and allergic sensitization.

Bioactive secondary metabolites from an endophytic fungus Phoma sp. PF2 derived from Artemisia princeps Pamp.

Two new isochromanone derivatives, (3S,4S)-3,8-dihydroxy-6-methoxy-3,4,5-trimethylisochroman-1-one (1) and methyl (S)-8-hydroxy-6-methoxy-5-methyl-4a-(3-oxobutan-2-yl)benzoate (2), together with six known compounds (3‒8) were isolated from the cultures of an endophytic fungus Phoma sp. PF2 obtained from Artemisia princeps. The chemical structures of the isolated compounds were elucidated by interpretation of spectroscopic data (1D, 2D NMR, HRESIMS, and CD) and calculation of ECD. All the isolated compounds (1‒8) showed moderate inhibitory activities on nitric oxide levels in lipopolysaccharide-induced RAW264.7 machrophage cells.

Arbuscular mycorrhizal symbiosis and achene mucilage have independent functions in seedling growth of a desert shrub.

Arbuscular mycorrhizal (AM) symbiosis can play a role in improving seedling establishment in deserts, and it has been suggested that achene mucilage facilitates seedling establishment in sandy deserts and that mucilage biodegradation products may improve seedling growth. We aimed to determine if AM symbiosis interacts with achene mucilage in regulating seedling growth in sand dunes. Up to 20 A M fungal taxa colonized Artemisia sphaerocephala roots in the field, and mycorrhizal frequency and colonization intensity exhibited seasonal dynamics. In the greenhouse, total biomass of AM fungal-colonized plants decreased, whereas the root/shoot ratio increased. AM symbiosis resulted in increased concentrations of nutrients and chlorophyll and decreased concentrations of salicylic acid (SA) and abscisic acid (ABA). Achene mucilage had a weaker effect on biomass and on nutrient, chlorophyll, and phytohormone concentration than did AM symbiosis. We suggest that AM symbiosis and achene mucilage act independently in enhancing seedling establishment in sandy deserts.

Rapid temporal changes in root colonization by arbuscular mycorrhizal fungi and fine root endophytes, not dark septate endophytes, track plant activity and environment in an alpine ecosystem.

Fungal root endophytes play an important role in plant nutrition, helping plants acquire nutrients in exchange for photosynthates. We sought to characterize the progression of root colonization by arbuscular mycorrhizal fungi (AMF), dark septate endophytes (DSE), and fine root endophytes (FRE) over an alpine growing season, and to understand the role of the host plant and environment in driving colonization levels. We sampled four forbs on a regular schedule from June 26th-September 11th from a moist meadow (3535 m a.s.l) on Niwot Ridge, Rocky Mountain Front Range, CO, USA. We quantified the degree of root colonization by storage structures, exchange structures, and hyphae of all three groups of fungi. AMF and FRE percent colonization fluctuated significantly over time, while DSE did not. All AMF structures changed over time, and the degree of change in vesicles differed by plant species. FRE hyphae, AMF arbuscules and AMF vesicles peaked late in the season as plants produced seeds. AMF hyphae levels started high, decreased, and then increased within 20 days, highlighting the dynamic nature of plant-fungal interactions. Overall, our results show that AMF and FRE, not DSE, root colonization rapidly changes over the course of a growing season and these changes are driven by plant phenology and seasonal changes in the environment.

Micropropagation and Cryoconservation of the Endangered Plant Species Artemisia laciniata (Asteraceae).

BACKGROUND: Artemisia laciniata, mainly distributed in Siberia and Central Asia, is classified as critically endangered in Europe. OBJECTIVES: This study developed a protocol for its micropropagation and cryopreservation. MATERIALS AND METHODS: In vitro cultures from fresh seed and in vivo shoots were initiated. Micropropagation and cryopreservation protocols were developed. Bacteria detected after cryopreservation were investigated using 16S rRNA analysis. Genome size measurements of regenerated plants after cryopreservation using flow cytometry and carbon isotope measurements to evaluate stress status were also carried out. RESULTS: A. laciniata from both starting materials could be successfully propagated on MS medium with 0.5 uM BAP. Material initiated from in vivo shoots yielded lower regeneration percentages (16%) after cryopreservation than material generated from seed (57 and 63%) using the droplet-vitrification method and PVS3. Bacteria occurring after cryopreservation belonged to the genera Sphingomonas, Staphylococcus, Curtobacterium and Gordonia. There was no significant difference in the genome size and stress status between non-cryopreserved and cryopreserved plants. CONCLUSION: A. laciniata could be readily micropropagated and cryopreserved. No negative effects of cryopreservation on plant water use efficiency or on genetic stability were found.

Study of artemisinin and sugar accumulation in Artemisia vulgaris and Artemisia dracunculus "hairy" root cultures.

We studied the effect of genetic transformation on biologically active compound (artemisinin and its co-products (ART) as well as sugars) accumulation in Artemisia vulgaris and Artemisia dracunculus "hairy" root cultures. Glucose, fructose, sucrose, and mannitol were accumulated in A. vulgaris and A. dracunculus "hairy" root lines. Genetic transformation has led in some cases to the sugar content increasing or appearing of nonrelevant for the control plant carbohydrates. Sucrose content was 1.6 times higher in A. vulgaris "hairy" root lines. Fructose content was found to be 3.4 times higher in A. dracunculus "hairy" root cultures than in the control roots. The accumulation of mannitol was a special feature of the leaves of A. vulgaris and A. dracunculus control roots. A. vulgaris "hairy" root lines differed also in ART accumulation level. The increase of ART content up to 1.02 mg/g DW in comparison with the nontransformed roots (up to 0.687 mg/g DW) was observed. Thus, Agrobacterium rhizogenes-mediated genetic transformation can be used for obtaining of A. vulgaris and A. dracunculus "hairy" root culture produced ART and sugars in a higher amount than mother plants.

CHEMOTYPIC Variation in Volatiles and Herbivory for Sagebrush.

Plants that are damaged by herbivores emit complex blends of volatile compounds that often cause neighboring branches to induce resistance. Experimentally clipped sagebrush foliage emits volatiles that neighboring individuals recognize and respond to. These volatiles vary among individuals within a population. Two distinct types are most common with either thujone or camphor as the predominate compound, along with other less common types. Individuals respond more effectively to cues from the same type, suggesting that some of the informative message is contained in the compounds that differentiate the types. In this study, we characterized the chemical profiles of the two common types, and we examined differences in their microhabitats, morphologies, and incidence of attack by herbivores and pathogens. Analysis by gas chromatography coupled with mass spectrometry revealed that the camphor type had higher emissions of camphor, camphene, and tricyclene, while the thujone type emitted more α-thujone, ß-thujone, (Z)-salvene, (E)-salvene, carvacrol, and various derivatives of sabinene. We were unable to detect any consistent morphological or microhabitat differences associated with the common types. However, plants of the thujone type had consistently higher rates of damage by chewing herbivores. One galling midge species was more common on thujone plants, while a second midge species was more likely to gall plants of the camphor type. The diversity of preferences of attackers may help to maintain the variation in volatile profiles. These chemical compounds that differentiate the types are likely to be informative cues and deserve further attention.

Desert Perennial Shrubs Shape the Microbial-Community Miscellany in Laimosphere and Phyllosphere Space.

Microbial function, composition, and distribution play a fundamental role in ecosystem ecology. The interaction between desert plants and their associated microbes is expected to greatly affect their response to changes in this harsh environment. Using comparative analyses, we studied the impact of three desert shrubs, Atriplex halimus (A), Artemisia herba-alba (AHA), and Hammada scoparia (HS), on soil- and leaf-associated microbial communities. DNA extracted from the leaf surface and soil samples collected beneath the shrubs were used to study associated microbial diversity using a sequencing survey of variable regions of bacterial 16S rRNA and fungal ribosomal internal transcribed spacer (ITS1). We found that the composition of bacterial and fungal orders is plant-type-specific, indicating that each plant type provides a suitable and unique microenvironment. The different adaptive ecophysiological properties of the three plant species and the differential effect on their associated microbial composition point to the role of adaptation in the shaping of microbial diversity. Overall, our findings suggest a link between plant ecophysiological adaptation as a "temporary host" and the biotic-community parameters in extreme xeric environments.

Consequences of inoculation with native arbuscular mycorrhizal fungi for root colonization and survival of Artemisia tridentata ssp. wyomingensis seedlings after transplanting.

In arid environments, the propagule density of arbuscular mycorrhizal fungi (AMF) may limit the extent of the plant-AMF symbiosis. Inoculation of seedlings with AMF could alleviate this problem, but the success of this practice largely depends on the ability of the inoculum to multiply and colonize the growing root system after transplanting. These phenomena were investigated in Artemisia tridentata ssp. wyomingensis (Wyoming big sagebrush) seedlings inoculated with native AMF. Seedlings were first grown in a greenhouse in soil without AMF (non-inoculated seedlings) or with AMF (inoculated seedlings). In spring and fall, 3-month-old seedlings were transplanted outdoors to 24-L pots containing soil from a sagebrush habitat (spring and fall mesocosm experiments) or to a recently burned sagebrush habitat (spring and fall field experiments). Five or 8 months after transplanting, colonization was about twofold higher in inoculated than non-inoculated seedlings, except for the spring field experiment. In the mesocosm experiments, inoculation increased survival during the summer by 24 % (p = 0.011). In the field experiments, increased AMF colonization was associated with increases in survival during cold and dry periods; 1 year after transplanting, survival of inoculated seedlings was 27 % higher than that of non-inoculated ones (p < 0.001). To investigate possible mechanisms by which AMF increased survival, we analyzed water use efficiency (WUE) based on foliar (13)C/(12)C isotope ratios (δ (13)C). A positive correlation between AMF colonization and δ (13)C values was observed in the spring mesocosm experiment. In contrast, inoculation did not affect the δ (13)C values of fall transplanted seedlings that were collected the subsequent spring. The effectiveness of AMF inoculation on enhancing colonization and reducing seedling mortality varied among the different experiments, but average effects were estimated by meta-analyses. Several months after transplanting, average AMF colonization was in proportion 84 % higher in inoculated than non-inoculated seedlings (p = 0.0042), while the average risk of seedling mortality was 42 % lower in inoculated than non-inoculated seedlings (p = 0.047). These results indicate that inoculation can increase AMF colonization over the background levels occurring in the soil, leading to higher rates of survival.

Allohumibacter endophyticus gen. nov., sp. nov., isolated from the root of wild Artemisia princeps (mugwort).

A novel actinobacterium designated strain MWE-A11T was isolated from the root of wild Artemisia princeps (mugwort). The isolate was aerobic, Gram-stain-positive and short rod-shaped, and the colonies were yellow and circular with entire margin. Strain MWE-A11T grew at 15-37 °C and pH 6.0-8.0. The predominant isoprenoid quinones were MK-11 and MK-10. The predominant fatty acids were anteiso-C15:0 and iso-C16:0, and the DNA G+C content was 68.8 mol%. The main polar lipids were diphosphatidylglycerol, phosphatidylglycerol and an unidentified glycolipid. The peptidoglycan contained 2,4-diaminobutyric acid as the diagnostic diamino acid, and the acyl type was glycolyl. Phylogenetic analyses based on 16S rRNA gene sequence comparisons indicated that strain MWE-A11T was affiliated with the family Microbacteriaceae, and was most closely related to the type strains of Humibacter antri (96.4% 16S rRNA gene sequence similarity), Herbiconiux moechotypicola (96.3%), Leifsonia soli (96.3%), Leifsonia lichenia (96.2%), Leifsonia xyli subsp. cynodontis (96.1%), Microbacterium testaceum (96.0%) and Humibacter albus (96.0%). However, the combination of chemotaxonomic properties clearly distinguished strain MWE-A11T from the related taxa at genus level. Accordingly, Allohumibacter endophyticus gen. nov., sp. nov. is proposed to accommodate a new member of the family Microbacteriaceae. The type strain of the type species is MWE-A11T (=JCM 19371T=KCTC 29232T).

Screening and identification of quorum sensing degraders from live feed Artemia.

Quorum sensing (QS) is bacterial cell-to-cell communication with small signal molecules such as acyl-homoserine lactones (AHL) that control a number of phenotypes including the regulation of virulence determinants in pathogenic bacteria. Therefore, quorum sensing degrader has been suggested as one of the biocontrol strategies to fight bacterial infections. In the present study, different bacterial QS degrader strains were isolated from Artemia and screened using Chromobacterium violaceum CV026 bioassay. The results showed that six bacterial strains (four Gram-positive and two Gram-negative) isolated from Artemia were able to degrade AHL in two different in vitro assays. All the strains were later identified through 16S rRNA gene sequencing as Rhodococcus opacus, Strepsporangium roseum, Streptomyces alboniger, Enterobacter clocae and Bacillus litoralis. Highest bacterial AHL degrader, Bacillus litoralis BP-ART/6 fully degraded 10 ppm AHL in 9 hrs. The present study showed that bacterial strains isolated from Artemia can act as a QS degrader. ?