Co-Lateral Effect of Octenidine, Chlorhexidine and Colistin Selective Pressures on Four Enterobacterial Species: A Comparative Genomic Analysis

Bacterial adaptation to antiseptic selective pressure might be associated with decreased susceptibility to antibiotics. In Gram-negative bacteria, some correlations between reduced susceptibility to chlorhexidine (CHX) and polymyxins have been recently evidenced in Klebsiella pneumoniae. In the present study, four isolates belonging to distinct enterobacterial species, namely K. pneumoniae, Escherichia coli, Klebsiella oxytoca and Enterobacter cloacae, were submitted to in-vitro selective adaptation to two antiseptics, namely CHX and octenidine (OCT), and to the antibiotic colistin (COL). Using COL as selective agent, mutants showing high MICs for that molecule were recovered for E. cloacae, K. pneumoniae and K. oxytoca, exhibiting a moderate decreased susceptibility to CHX, whereas OCT susceptibility remained unchanged. Using CHX as selective agent, mutants with high MICs for that molecule were recovered for all four species, with a cross-resistance observed for COL, while OCT susceptibility remained unaffected. Finally, selection of mutants using OCT as selective molecule allowed recovery of K. pneumoniae, K. oxytoca and E. cloacae strains showing only slightly increased MICs for that molecule, without any cross-elevated MICs for the two other molecules tested. No E. coli mutant with reduced susceptibility to OCT could be obtained. It was therefore demonstrated that in-vitro mutants with decreased susceptibility to CHX and COL may be selected in E. coli, K. pneumoniae, K. oxytoca and E. cloacae, showing cross-decreased susceptibility to COL and CHX, but no significant impact on OCT efficacy. On the other hand, mutants were difficult to obtain with OCT, being obtained for K. pneumoniae and E. cloacae only, showing only very limited decreased susceptibility in those cases, and with no cross effect on other molecules. Whole genome sequencing enabled deciphering of the molecular basis of adaptation of these isolates under the respective selective pressures, with efflux pumps or lipopolysaccharide biosynthesis being the main mechanisms of adaptation.

Multi-Step Cellular and Tissue Selection of Soybean for Resistance to Osmotic Stress Using Peg 6000 Invitro Conditions

Cell and tissue selection in vitro allows targeted selection of the desired traits under severe selective conditions at the level of individual cells and tissues. On the basis of multistage cell and tissue selection with the use of a selective agent - neutral osmotic polyethylene glycol 6000 in increasing concentrations -5%, 10%, 15%, 20% of the final volume of the nutrient medium, callus of the Zhansaya soybean variety that are stably resistant to osmotic stress have been obtained. Regeneration from callus was noted only in8.3 % of the planted callus 6 soybean regenerants plants resistant to osmotic stress were obtained from callus.

Screening and selection of camptothecin producing endophytes from Nothapodytes nimmoniana

Endophytic fungi with the ability to produce plant based secondary metabolites are a potential alternative for producing the host plant metabolite and to prevent natural plants from extinction. To isolate a high metabolite yielding endophytic strain from plants, hundreds of endophytic strains are screened and tested for product yield separately under axenic state, before shortlisting the potential endophyte, which involves huge time consumption. In this study, strategies for screening and selection of high camptothecin yielding endophytes from their natural habitat were proposed. A correlation was built between the camptothecin yield in the explants and the endophytes isolated from them. In addition, camptothecin yield was compared between the endophytes isolated from young and matured plants. Further, camptothecin producers and non-producers strains were compared for their tolerance toward camptothecin. The study indicates that high camptothecin yielding endophytes were isolated from high yielding explants and younger plants and they were more tolerant to camptothecin in comparison to non-camptothecin yielding endophytes. Thus, choosing a young and high yielding explant for endophyte isolation, and use of camptothecin as a selective agent in the growth medium, can be instrumental in screening and selection of high camptothecin yielding endophytes from nature in relatively less time.

Perception-driven dynamics of mimicry based on attractor field model

We provide a formal account of an interface that bridges two different levels of dynamic processes manifested by mimicry: prey–prey interactions and predators' perception. Mimicry is a coevolutionary process between an animate selective agent and at least two similar organisms selected by agent's perception-driven actions. Attractor field model explains perceived similarity of forms by noting that in both human and animal cognition, morphologically intermediate forms are more likely to be perceived as belonging to rare rather than abundant forms. We formalize this model in terms of predators' perception space deformation using numerical simulations and argue that the probability of confusion between similar species creates pressure on the perception space, which in turn leads to inflation of regions of perception space with high density of species representations. Such inflation causes increased discrimination between species by a predator, which implies that adaptive mimicry could initially emerge more easily among atypical species because they do not need the same level of similarity to the model. We provide a theoretical instrument to conceptualize interdependence between objective measurable matrices and perceived matrices of the same external reality. We believe that our framework leads to a more precise understanding of the evolution of mimicry.

USE OF SUCROSE AND MANNITOL FOR DIFFERENTIATION OF FLAX GENOTYPES BY RESISTANCE TO OSMOTIC STRESS

The studies were carried out with the aim of studying the effect of various concentrations of sucrose and mannitol on seeds, immature embryos, and callus cultures of flax to develop a method for obtaining genotypes resistant to osmotic stress. The work was carried out in the Tver region in the laboratory of breeding technologies in 2017–2019. Flax varieties Barbara, Belinka, LM-98, Aurore, Tverskoy, Svetoch, Diplomat, Symfonia were used as objects of research. The seeds were obtained from the National Flax Collection of the Federal Scientific Center for Bast Crops. The effect of sucrose solution on the length of the primary root was detected at concentrations - 0; 8.7; 14.9%. To assess the germination energy of seeds under osmotic stress, the concentration of sucrose was reduced and the range 0 (control) ... 9% was considered. Immature embryos removed from the capsules on the 10th day after pollination were cultivated on MS medium with sucrose, as a selective agent, at a concentration of 5.0 ... 7.0%. Callus tissues were cultured using mannitol as an osmotic at concentrations of 0; 30.0; 36.4; 37.0; 37.4; 38.0 mg/l. Concentrations of 5.0, 6.0 and 7.0% of sucrose can be used as an osmotic differentiator for seeds (10 ... 80% of seeds germinated in the Belinka variety, 80 ... 100% in the Varbara variety, 80 ... 90% in the variety LM-98). Sucrose, as a selective agent, in a culture of immature flax embryos in vitro at a concentration of 5.0 ... 7.0% can be selective only for certain genotypes, for example, the Aurore variety. The selection of resistant callus cells, followed by the formation of adventive buds and shoots in the meristematic foci, can be carried out on media containing 30.0 or 36.4 mg / L of osmosis, which allows obtaining morphogenic callus, buds, shoots in all studied genotypes, as well as in the Aurore variety 1.1 ... 1.2 byp./callus, in the Tverskoy variety - 0.6 ... 0.8, in the Barbara variety - 1.0 ...1.1

Glyphosate selection of maize transformants containing CP4epsps gene

Aim. To study the selection conditions of maize transformants containing the CP4epsps gene using glyphosate as a selective agent. Methods. Tissue culture in vitro, Agrobacterium-mediated transformation, selection of transgenic plants, isolation of total plant DNA, analysis of plant DNA by polymerase chain reaction (PCR). Results. The morphogenic maize callus of immature embryos of the hybrid (PLS61)R2×PLS61 was produced, which had a high regeneration rate (up to 95%), that persisted over long cultivation. Agrobacterium mediated transformation of the morphogenic callus and selection of the transgenic material using glyphosate yielded maize transformants containing the CP4epsps gene at a frequency of 1%. Conclusions. Maize genotype (PLS61)R2×PLS61 is promising for studies on the maize genetic transformation, in particular for the production of transgenic maize resistant to glyphosate herbicide. The use of morphogenic maize callus (PLS61)R2×PLS61 and glyphosate as a selective agent at a concentration of 0.1 mM and 0.25 mM in media for callusogenesis and 0.01 mM in the medium for regeneration was effective for the selection of transgenic plants with the gene CP4epsps. Keywords: Zea mays L., morphogenic callus, Agrobacterium-mediated transformation, PCR, genetic engineering.

Hiding in plain sight: experimental evidence for birds as selective agents for host mimicry in mistletoes

Many Australian mistletoe species are cryptic, closely resembling their host foliage and overall appearance. Seed-dispersing birds have been proposed as a selective agent for host resemblance, with cryptic mistletoes only located by thoroughly searching through canopies regardless of infection status, boosting mistletoe populations by increasing the frequency of seeds dispersed to uninfected hosts; however, this idea is as yet untested. We measured bird visitation to fruiting mistletoes (n = 20) over two consecutive days, with manual defoliation of the mistletoe occurring before observation began on the second day to determine the effect of the visual appearance of the mistletoe on potential seed-dispersing birds, expecting defoliation to reduce the number of visits. Visits to the mistletoes were compared between days of observation and dietary guild (mistletoe specialist/nonspecialist). Intact mistletoes were visited more than the defoliated mistletoes, and the dietary guilds differed in their visitation patterns. This work demonstrates that the visual acuity of seed-dispersers can distinguish subtle differences in mistletoe phenotypes within infected hosts, consistent with the hypothesis that those mistletoes that more closely resemble their hosts are more difficult to perceive from afar and therefore more likely to have their seeds dispersed to uninfected hosts.