Interaction of bacteriophage P1 with an epiphytic Pantoea agglomerans strain-the role of the interplay between various mobilome elements.

P1 is a model, temperate bacteriophage of the 94 kb genome. It can lysogenize representatives of the Enterobacterales order. In lysogens, it is maintained as a plasmid. We tested P1 interactions with the biocontrol P. agglomerans L15 strain to explore the utility of P1 in P. agglomerans genome engineering. A P1 derivative carrying the Tn9 (cmR) transposon could transfer a plasmid from Escherichia coli to the L15 cells. The L15 cells infected with this derivative formed chloramphenicol-resistant colonies. They could grow in a liquid medium with chloramphenicol after adaptation and did not contain prophage P1 but the chromosomally inserted cmR marker of P1 Tn9 (cat). The insertions were accompanied by various rearrangements upstream of the Tn9 cat gene promoter and the loss of IS1 (IS1L) from the corresponding region. Sequence analysis of the L15 strain genome revealed a chromosome and three plasmids of 0.58, 0.18, and 0.07 Mb. The largest and the smallest plasmid appeared to encode partition and replication incompatibility determinants similar to those of prophage P1, respectively. In the L15 derivatives cured of the largest plasmid, P1 with Tn9 could not replace the smallest plasmid even if selected. However, it could replace the smallest and the largest plasmid of L15 if its Tn9 IS1L sequence driving the Tn9 mobility was inactivated or if it was enriched with an immobile kanamycin resistance marker. Moreover, it could develop lytically in the L15 derivatives cured of both these plasmids. Clearly, under conditions of selection for P1, the mobility of the P1 selective marker determines whether or not the incoming P1 can outcompete the incompatible L15 resident plasmids. Our results demonstrate that P. agglomerans can serve as a host for bacteriophage P1 and can be engineered with the help of this phage. They also provide an example of how antibiotics can modify the outcome of horizontal gene transfer in natural environments. Numerous plasmids of Pantoea strains appear to contain determinants of replication or partition incompatibility with P1. Therefore, P1 with an immobile selective marker may be a tool of choice in curing these strains from the respective plasmids to facilitate their functional analysis.

Transcriptomic Changes in Medicago truncatula and Lotus japonicus Root Nodules during Drought Stress.

Drought is one of the major environmental factors limiting biomass and seed yield production in agriculture. In this research, we focused on plants from the Fabaceae family, which has a unique ability for the establishment of symbiosis with nitrogen-fixing bacteria, and are relatively susceptible to water limitation. We have presented the changes in nitrogenase activity and global gene expression occurring in Medicago truncatula and Lotus japonicus root nodules during water deficit. Our results proved a decrease in the efficiency of nitrogen fixation, as well as extensive changes in plant and bacterial transcriptomes, shortly after watering cessation. We showed for the first time that not only symbiotic plant components but also Sinorhizobium meliloti and Mesorhizobium loti bacteria residing in the root nodules of M. truncatula and L. japonicus, respectively, adjust their gene expression in response to water shortage. Although our results demonstrated that both M. truncatula and L. japonicus root nodules were susceptible to water deprivation, they indicated significant differences in plant and bacterial response to drought between the tested species, which might be related to the various types of root nodules formed by these species.

Ecological risk assessment for land contaminated by petrochemical industry.

Contamination with harmful chemical substances, including organic compounds of the BTEX and PAH groups, constitutes one of the major threats to the functioning of soil habitat. Excessive contents of the above substances can exert adverse effects on soil organisms, reduce biodiversity, and thus deteriorate soil quality. The threat to soil ecosystems within areas particularly exposed to contamination with accumulating chemical compounds was assessed using the Ecological Risk Assessment (ERA) with a multi-stage Triad (triage rapid initial assessment) procedure (taking into account the different lines of evidence). The article presents the results of chemical and ecotoxicological study of soils sampled at sites affected by contamination from petrochemical industry. The study results provided foundations for developing the site specific ERA framework for the area examined.

Endophytic Detection in Selected European Herbal Plants.

A total of 181 cultivable endophytic bacterial isolates were collected from stems of 13 species of herbs inhabiting Europe (Poland): Chelidonium majus L., Elymus repens L., Erigeron annuus L., Euphrasia rostkoviana Hayne, Foeniculum vulgare L., Geranium pratense L., Humulus lupulus L., Matricaria chamomilla L., Mentha arvensis L., Papaver rhoeas L., Rosmarinus officinalis L., Solidago gigantea L. and Vinca minor L. The isolates were screened for their antifungal activity and fifty three were found to inhibit fungal growth. Of these, five had strong antifungal properties. These selected isolates were identified as: Pseudomonas azotoformans, P. cedrina, Bacillus subtilis group and Erwinia persicina.

Isolation and characterization of bacterial endophytes of Chelidonium majus L.

The aim of this study was to isolate and identify endophytic bacteria from stems of Chelidonium majus L. (greater celandine) and to evaluate their antifungal properties. In total, 34 bacterial endophyte strains were isolated. The fungistatic effects of these bacteria on the growth of five moulds (Alternaria alternata, Chaetonium sp., Paecilomyces variotti, Byssochlamys fulva, Aureobasidium pullulans) and one species of black yeast (Exophiala mesophila) were tested. The majority of the bacterial isolates were found to inhibit the growth of fungi and those with the strongest antifungal properties were further characterized. Of the twelve isolates examined, 11 were species of Bacillus thuringiensis and one was Bacillus amyloliquefaciens.

Characterization of selected groups of microorganisms occurring in soil rhizosphere and phyllosphere of oats.

Studies were carried out on the microflora of phyllosphere and soil rhizosphere of hulled (Chwat variety) and naked (Akt variety) oats. The material taken for study embraced samples of leaves and soil rhizosphere taken from cultivations differing in extent of nitrogen fertilization. The studies involved determination of total number of aerobic heterotrophic bacteria belonging to the genus Pseudomonas and microscopic hyphal fungi. Qualitative determinations focused on bacteria belonging to the genera Azotobacter and Azospirillum were also made. Our results point to differences in number of microscopic hyphal fungi in the phyllosphere of both varieties of oats, depending on nitrogen fertilization dose. However, there were no significant differences in the number of bacteria of the different genera determined in the phyllosphere and rhizosphere. Strains of oligonitrophilic and diazotrophic bacteria were isolated from samples of the phyllosphere of oats and their N2-fixing activity was determined by the acetylene reduction method using gas chromatography.

Effect of addition of "Greenline" preparations to feed mixtures for broilers on the composition of their intestinal microflora.

The current study deals with the possibility of replacing the antibiotic growth stimulator avilamycin, a mixture of oligosaccharides of the orthosomycin group, with the herbal preparations Greenline 1 and 2. The microbiological part of the study embraced examination of the intestinal microflora of broilers. The birds in the study belonged to four experimental groups, distinguished on the basis of feed supplements used. For the microbiological determination five birds from each group were selected at random and the contents of their small intestine was examined for given groups of microorganisms. The remaining birds in each group were examined and evaluated on the basis of zootechnical indices. Our results suggest that Greenline 1 efficiently eliminates certain pathogenic bacteria, above all lactose-positive bacteria belonging to the family Enterobacteriaceae and Staphylococci. It seems that the presence of Greenline 1 in the feed mix used enhances the colonisation of the mucous membrane of the studied chicken with Lactobacillus lactic acid bacteria. This is indicated by the considerably higher number of these bacteria in the small intestine of the birds receiving the supplement Greenline 1.