La rizobacteria promotora del crecimiento vegetal Arthrobacter agilis UMCV2 coloniza endofíticamente a Medicago truncatula / The plant growth-promoting rhizobacterium Arthrobacter agilis UMCV2 endophytically colonizes Medicago truncatula

Arthrobacter agilis UMCV2 es una bacteria rizosférica que promueve el crecimiento vegetal de plantas leguminosas proveyéndoles hierro soluble. Un segundo mecanismo de promoción se da a través de la producción de compuestos volátiles que estimulan los mecanismos de absorción de hierro. Adicionalmente, A. agilis UMCV2 tiene la capacidad de inhibir el crecimiento de organismos fitopatógenos. En el presente trabajo se emplea una combinación de las técnicas de reacción en cadena de la polimerasa cuantitativa e hibridación in situ con fluorescencia para detectar y cuantificar la presencia de la bacteria en los tejidos internos de la planta leguminosa Medicago truncatula. Nuestros resultados demuestran que A. agilis UMCV2 se comporta como una bacteria endófita de M. truncatula especialmente en medios donde el hierro está disponible.

Arthrobacter agilis UMCV2 is a rhizosphere bacterium that promotes legume growth by solubilization of iron, which is supplied to the plant. A second growth promotion mechanism produces volatile compounds that stimulate iron uptake activities. Additionally, A. agilis UMCV2 is capable of inhibiting the growth of phytopathogens. A combination of quantitative polymerase chain reaction and fluorescence in situ hybridization techniques were used here to detect and quantify the presence of the bacterium in the internal tissues of the legume Medicago truncatula. Our results demonstrate that A. agilis UMCV2 behaves as an endophytic bacterium of M. truncatula, particularly in environments where iron is available.

Screening and characterization of endophytic Bacillus and Paenibacillus strains from medicinal plant Lonicera japonica for use as potential plant growth promoters

Abstract A total of 48 endophytic bacteria were isolated from surface-sterilized tissues of the medicinal plant Lonicera japonica, which is grown in eastern China; six strains were selected for further study based on their potential ability to promote plant growth in vitro (siderophore and indoleacetic acid production). The bacteria were characterized by phylogenetically analyzing their 16S rRNA gene similarity, by examining their effect on the mycelial development of pathogenic fungi, by testing their potential plant growth-promoting characteristics, and by measuring wheat growth parameters after inoculation. Results showed that the number of endophytic bacteria in L. japonica varied among different tissues, but it remained relatively stable in the same tissues from four different plantation locations. Among the three endophytic strains, strains 122 and 124 both had high siderophore production, with the latter showing the highest phosphate solubilization activity (45.6 mg/L) and aminocyclopropane-1-carboxylic acid deaminase activity (47.3 nmol/mg/h). Strain 170 had the highest indoleacetic acid (IAA) production (49.2 mg/L) and cellulase and pectinase activities. After inoculation, most of the six selected isolates showed a strong capacity to promote wheat growth. Compared with the controls, the increase in the shoot length, root length, fresh weight, dry weight, and chlorophyll content was most remarkable in wheat seedlings inoculated with strain 130. The positive correlation between enzyme (cellulose and pectinase) activity and inhibition rate on Fusarium oxysporum, the IAA production, and the root length of wheat seedlings inoculated with each tested endophytic strain was significant in regression analysis. Deformity of pathogenic fungal mycelia was observed under a microscope after the interaction with the endophytic isolates. Such deformity may be directly related to the production of hydrolytic bacterial enzymes (cellulose and pectinase). The six endophytic bacterial strains were identified to be Paenibacillus and Bacillus strains based on the results of 16S rRNA gene sequencing analysis and their physiological and biochemical characteristics. Results indicate the promising application of endophytic bacteria to the biological control of pathogenic fungi and the improvement of wheat crop growth.

PRELIMINARY STUDY ON THE COLONIZATION OF ENDOPHYTIC BACTERIUM 01-144 IN TOMATO ROOT AND STEM / 微生物学通报

The endophytic bacterum 01-144 was marked by using the method of antib iotic-resistance. Colonization of 01-144 in tomato root and stem was investig ate d. Result showed that 01-144 colonized in the root and stem and the colonizing a bility in the root was stronger than in the stem after dipping seed or watering root treatmeat, It was also found that this bacterium could more easly colonized in the low stem than in the upper stem. The population fluctuation of 01-144 ha d the same trend in both root and stem i.e.first increased then decreasing, an d the fluctuation in the root was more even than in the stem.

Isolation and Identification of Endophytic Bacteria H-6 with High Antifungal Activity from Huperzia serrata / 微生物学通报

In this study,nearly 200 endophytic bacteria were isolated from different part of Huperzia serrata, over 60 bacterium with clear antifungal activity were selected from those cultures.Among them,strain H-6 exhibited the highest antifungal activity which was strongly inhibits the growth of many plant pathogenic fungi such as Sclerotinia scleroliorum,Fusarium graminearumt,Sclerotinia libertiana,Phytophthora capsici Leonia and Sesame fusarium wilt.According to the characteristics of morphology,physiology and biochem- istry tests and the comparison of 16S rDNA sequence,the strain H-6 was similar to the Burkholderia.So strain H-6 was identified as Burkholderia sp.H-6.The results also showed that Burkholderia sp.H-6 was markedly different from Burkholderia cepacia that was applied widely in agriculture as antagonistic bacteria. The medium and culture conditions of the strain all were optimized by single factor and orthogonal experiments.In the investigation of the culture condition,growth was carried out in a basal medium(potato juice)and gradually supplemented with the various ingredients to be investigated.The major ingredients be- ing investigated included carbon sources and nitrogen sources.The optimal antifungal activity production condition is growth in a medium(potato juice with 2.5%mannitol and 0.1%NaNO3),initial pH 4.0 at 28℃.