Frateuria defendens reduces yellows disease symptoms in grapevine under field conditions

Yellows diseases in grapevine, associated with the presence of different phytoplasmas, are a major problem for growers, with no environmentally friendly means of control. Frateuria defendens (Frd), a bacterium with endophytic traits, has been shown to reduce yellows symptoms in grapevine plantlets under laboratory conditions. The objective of this study was to test whether similar effects could be achieved under field conditions. A trial was conducted in a heavily infected vineyard in northern Israel for two consecutive years. A suspension of Frd cells (108·mL-1) was applied bi-weekly by foliar spray on grapevines from bud burst to leaf senescence. Frd penetrated the leaves during the growing period but not during leaf senescence and could be detected in the leaves by PCR analysis up to 14 days post-spraying. The rate of yellows infection was lower in the treated grapevines compared to its increase in untreated grapevines and the yield of symptomatic plants was improved by 10 to 20 %. Taken together, the results suggest Frd acted as a biological control agent in vineyards under the experimental conditions tested

Microbe Relationships with Phytoplasmas in Plants and Insects

The hosts of phytoplasmas, i.e. plants and insect vectors, are inhabited by diverse microorganisms having interactions spanning from mutualism to parasitism. When the pathogens colonize a host, they may thus be exposed to diverse interac- tions with complex microbial communities. These relations are still poorly recog- nized for phytoplasmas, even though many beneficial or harmful interactions have been described for other plant pathogens. The knowledge on traits of microbial relations involving phytoplasmas in insects and plants is regarded as a valuable tool for designing new control methods against the diseases associated with these patho- gens, by displaying direct antagonistic activities, altering the vector fitness or com- petence for transmission, or promoting plant immune response or growth. In insect vectors, which mainly host bacterial associates, with few yeast-like symbionts, direct interactions with phytoplasmas were described for bacteria of the genera Frauteria in Hyalesthes obsoletus and Asaia in Euscelidius variegatus. In plants, the most studied systems are grapevine, apple and coconut palm, along with model organisms such as Catharanthus roseus and in vitro micropropagated plants. Here, many bacteria, mainly of the genera Pseudomonas, Burkholderia and Paenibacillus, as well as the fungal endophyte Epicoccum nigrum, were shown to inhibit phyto- plasma growth and related symptoms in the plant hosts. Overall, the recent advances concerning the knowledge on microbial symbioses in phytoplasma plant and insect hosts can consistently support future research regarding the phytoplasma infection process, and eventually drive new control strategies against phytoplasma-associated diseases

Isolation and Bioaugmentation of an Estradiol-Degrading Bacterium and Its Integration into a Mature Biofilm▿

Bioaugmentation can alter the potential activity as well as the composition of the naturally occurring microbial biota during bioremediation of a contaminated site. The focus of the current study is the pollutant 17β-estradiol (E2), which can cause endocrine effects and is potentially harmful to aquatic biota and to public health. The community composition and function of biofilms, originating from a wetland system, as affected by augmentation of an estradiol-degrading bacterium (EDB-LI1) under different conditions, were investigated. EDB-LI1 inoculation into biofilm from two wetland ponds representing early and advanced water treatment stages, respectively, yielded three significant observations, as follows: (i) EDB-LI1, enriched from a biofilm of a constructed wetland wastewater treatment system, was detected (by quantitative PCR [qPCR] analysis) in this environment in the augmented biofilm only; (ii) the augmented biofilm acquired the ability to remove estradiol; and (iii) the bacterial community composition (analyzed by PCR-denaturing gradient gel electrophoresis [DGGE]) of the augmented biofilm differed from that of the control biofilm. Furthermore, EDB-LI1 bioaugmentation showed a higher level of removal of estradiol with biofilms that originated from the advanced-treatment-stage wetland pond than those from the early-treatment-stage pond. Hence, the bioaugmentation efficiency of EDB-LI1 depends on both the quality of the feed water and the microbial community composition in the pond