ISOLATION AND IDENTIFICATION OF RHIZOBACTERIA FROM MAIZE (ZEA MAYS L.) IN LUVISOLS AND DOCUMENTATION THEIR PLANT GROWTH PROMOTING TRAITS

There is a growing interest in the issue of inoculation of rhizobacteria into the agricultural soil because this group of bacteria can  increase  productivity and quality of  agriculturally important crop and contributes to the stability of agroecosystems. The aim of our work was to isolate and characterize of plant growth promoting traits (production of IAA, siderophores, phosphate solubilisation, antifungal activity) of rhizobacteria belonging to a group of plant growth promoting rhizobacteria (PGPR), and isolated from rhizosphere of maize (Zea mays L.) in luvisols.  Quantitative representation of rhizobacteria of maize was 7.4 . 106 CFU.g-1 dry soil. A total of eleven species of maize rhizosphere where isolated and confirmed as PGPR in vitro. The  all  isolates  showed positive indole-3-acetic acid (IAA) production ranging between 1.39 and 15.74 µg.ml-1. Seven  strains (63.6  %) has been shown with low and 1 strain with intermediate solubilisation index of phosphates and the  positive production of siderophores showed  7 isolates (63, 6 %). Except for the isolate KmiJP17B089, all others inhibited the growth of Sclerotinia sclerotiorum and Rhizoctonia solani by more than 50 %. In the case of Fusarium graminearum, on the other hand, we observed a very low inhibitory activity. The most active  in observed traits were  three isolates identified by the 16S rRNA gene sequencing and NCBI database using the BLAST  resource as Bacillus altitudinis strain KmiJP17B089, Bacillus aryabhattai strain KmiJP17B090  and  Bacillus megaterium strain KmiJP17B091. These results suggest the possibility to tested in vivo these Bacillus species as potential biological fertilizer  to increase maize production.

Effects of sulfonylurea herbicides chlorsulfuron and sulfosulfuron on enzymatic activities and microbial communities in two agricultural soils

Sulfonylurea herbicides are widely used for weed control in agriculture, and they are suspected to alter microbial communities and activities in the soil. This study investigates the impact of two sulfonylurea herbicides chlorsulfuron and sulfosulfuron on microbial community and activity in two different soils taken from two sites in west part of the Slovak Republic. The soil from the Malanta site was silt-loam luvisol with pH_(H2O) 5.78 while the soil from the Stefanov site was sandy-loam regosol with pH_(H2O) 8.25. These soils were not treated by sulfonylurea herbicides at least for 2 years prior to the study. In laboratory assay, the herbicides were applied to soil in their maximal recommended doses 26 and 25 g per hectare of chlorsulfuron and sulfosulfuron, respectively. Their effect was evaluated on the 3rd, 7th, 14th, 28th, 56th, and 112th day after application to soil. Illumina high-throughput amplicon sequencing of the 16S rRNA gene and ITS region was used to monitor changes on prokaryotic and fungal community composition. Enzymatic activity was evaluated using 11 substrates. Physiological profile of microbial community was analyzed using Biolog© ecoplates. Significant changes in enzymatic activity caused by the application of herbicides were found during the first 28 days. The application of herbicides altered the activity of cellobiohydrolase, arylsulphatase, dehydrogenase, phosphatase, and FDA hydrolase. Chlorsulfuron caused a more varying response of enzymatic activity than sulfosulfuron, and observed changes were not the same for both soils. In Malanta soil, chlorsulfuron decreased dehydrogenase activity while it was increased in the Stefanov soil. Phosphatase activity was decreased in both soils on 7th and 14th day. There were only minor changes in prokaryotic or fungal community or physiological profiles regarding pesticide application. Differences between soils and incubation time explained most of the variability in these parameters. Diversity indices, physiological parameters, and enzymatic activity decreased over time. The results have shown that chlorsulfuron and sulfosulfuron can affect the function and activity of the soil microbial community without significant change in its composition.

Escherichia coli as a carrier of tetracyclines and penicillins resistance in wild pheasant (Phasianus colchicus)

Wild animals like pheasant seem to be a good source of information about human activities. Therefore, the wild pheasants and relative stable appendix microcenosis were selected for antibiotic resistance testing. Penicillin resistance by MALDI-TOF Mass Spectrometry and tetracyclines resistance by genetic methods using specific primers were tested. Differences between tetracycline and penicillin resistance were detected. Results showed high prevalence of resistant Escherichia coli isolated from wild pheasant appendix. E. coli isolated from wild pheasant appendix carried plasmids for penicillins and tetracyclines resistance where they were responsible for enzymatic degradation of penicillin and carried genes for regulating efflux pumps for tetracyclines. Results showed that tetracyclines and penicillins resistance is widespread between wild pheasants with a carrier as Escherichia coli isolated from relative stable microcenosis of appendix.