Phyto-Beneficial Traits of Rhizosphere Bacteria: In Vitro Exploration of Plant Growth Promoting and Phytopathogen Biocontrol Ability of Selected Strains Isolated from Harsh Environments.

Beneficial interactions between plants and some bacterial species have been long recognized, as they proved to exert various growth-promoting and health-protective activities on economically relevant crops. In this study, the growth promoting and antifungal activity of six bacterial strains, Paenarthrobacter ureafaciens, Beijerinckia fluminensis, Pseudomonas protegens, Arthrobacter sp., Arthrobacter defluii, and Arthrobacter nicotinovorans, were investigated. The tested strains resulted positive for some plant growth promoting (PGP) traits, such as indole-3-acetic acid (IAA), 1-aminocyclopropane-1-carboxylate-deaminase (ACC-deaminase), siderophore production, and solubilization of phosphates. The effect of the selected bacteria on Arabidopsis thaliana seedlings growth was assessed using different morphological parameters. Bacterial activity against the phytopathogenic fungal species Aspergillus flavus, Fusarium proliferatum, and Fusarium verticillioides was also assessed, since these cause major yield losses in cereal crops and are well-known mycotoxin producers. Strains Pvr_9 (B. fluminensis) and PHA_1 (P. protegens) showed an important growth-promoting effect on A. thaliana coupled with a high antifungal activity on all the three fungal species. The analysis of bacterial broths through ultra performance liquid chromatography-mass spectrometry (UPLC-MS) and liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS/MS) confirmed the presence of potential PGP-compounds, among these are desferrioxamine B, aminochelin, asperchrome B, quinolobactin siderophores, and salicylic acid.

Cytotoxic activity of copper(ii), nickel(ii) and platinum(ii) thiosemicarbazone derivatives: interaction with DNA and the H2A histone peptide.

Metal complexes still represent promising pharmacological tools in the development of new anticancer drugs. Bis(citronellalthiosemicarbazonate)nickel(ii) is a metal compound extremely effective against leukemic and NCS cancer cell lines. Preliminary experiments performed with this compound and with its Cu(ii) and Pt(ii) analogues evidenced alterations, detectable by comet assay, in the DNA of treated U937 cells. In addition, [Cu(tcitr)2] and [Pt(tcitr)2] were also able to induce gene mutations and produce frameshift events. To gain further insights into the mechanism of action of these metal compounds, we carried out a multidisciplinary study to investigate whether their biological activity can be ascribed to the direct interaction with DNA or with chromatin. The DNA interaction was investigated by means of CD and UV-Vis spectroscopic techniques and by AFM, whereas the chromatin interaction was studied by analyzing the effects of the compounds on the structure of a peptide that mimicks the potential metal binding site in the "C-tail" region of histone H2A by means of NMR, CD, UV-Vis and MS. The intensities of the effects induced by the metal compounds on the peptide follow the order [Ni(tcitr)2] > [Pt(tcitr)2] ≫ [Cu(tcitr)2]. From the AFM data, a remarkable DNA compaction was observed in the presence of [Pt(tcitr)2], while [Ni(tcitr)2] causes the formation of large interlaced DNA aggregates.

Advantages in exploring a new environment with the left eye in lizards.

Lizards (Podarcis muralis) preferentially use the left eye during spatial exploration in a binocular condition. Here we allowed 44 adult wild lizards to explore an unknown maze for 20 min under a temporary monocular condition whilst recording their movements, particularly the direction of turns made whilst walking within the maze. Lizards with a patch on their right eye, i.e. using their left eye to monitor the environment, moved faster than lizards with a patch on their left eye when turning both leftward and rightward in a T-cross. Hence, right eye-patched lizards were faster than left eye-patched lizards also in turning right, although their right eye was covered. Thus, lizards that could use the left eye/right hemisphere to attend spatial cues appeared to have more control and to be more prompt in exploring the maze. In addition, female lizards with their left eye covered stopped very frequently when they reached crosses, showing a high level of indecision. Results confirm that P. muralis lizards using their left eye only in exploring a new environment react faster and more efficiently than those using the right eye only in exploration. Hence lateralisation of spatial stimuli mediated by the left eye/right hemisphere could provide an advantage to this species.

Looking at a predator with the left or right eye: asymmetry of response in lizards.

Studies carried out with the common wall lizard (Podarcis muralis) revealed preferential use of the left eye during responses to predatory threat in laboratory settings and in the wild. Here we tested lizards under monocular conditions of vision, using temporary eye-patching. Lizards were facing a (simulated) predatory threat laterally, from the side of the non-patched eye. Results showed that lizards with the left eye uncovered during predatory threat used the left eye to monitor the predator, whereas lizards with the right eye uncovered nonetheless tried to use the covered left eye. Moreover, lizards frequently tried to change the eye exposition, making a body C-bend behaviour. Right-eyed lizards showed more frequent and faster C-bending responses than left-eyed lizards, trying to monitor the predator with the left eye even though it was patched. Results fit with asymmetries in spontaneous eye use observed in laboratory conditions and in the wild in this species, confirming that structures located on the right side of the brain (mainly served by the left eye) predominantly attend to predatory threat.

Is the Podarcis muralis lizard left-eye lateralised when exploring a new environment?

The typical lateral eye position in ectotherms likely facilitated the spread of visual lateralisation--i.e., the different use of the eyes--in those species. The diffusion of this form of lateralisation seems due to the possibility of carrying out more than one task simultaneously, some controlled by one eye and the visual structures it feeds and some by the other. Similar to other species, exploratory and monitoring behaviours seem to be under left "eye system" control. Wild individuals of the Common wall lizard Podarcis muralis were tested individually in captivity to ascertain whether they showed lateralisation when exploring a new environment, using preferentially the left eye. In Experiment 1, the lizards explored a maze. A left-turning bias was found, both at individual and population level, indicating a possible right hemisphere visual control. In Experiment 2, lizards explored a T-maze, preferring to enter the left rather than the right arm though without any particular preference in the head turns. In Experiment 3, the lizards had to exit an opaque box within a terrarium. We found a left-eye preference again for head turn while leaving the box. Our findings support the hypothesis of right hemisphere mediation of exploratory and monitoring behaviours in Podarcis muralis. In addition to previous studies on the same species, our results support the hypothesis of a simultaneous control of anti-predatory and exploratory behaviours (left-eye mediated) and predatory behaviour (right-eye mediated).

Complementary lateralisation in the exploratory and predatory behaviour of the common wall lizard (Podarcis muralis).

Several ectotherms show lateralisation, particularly visual lateralisation. Such brain specialisation has an ancient origin and is still present in living vertebrates. One important advantage is the possibility for lateralised animals to carry out two tasks at the same time, without altering the efficiency of either one. Recent studies on the common wall lizard (Podarcis muralis) found right eye/left hemisphere bias for attention to the cues of prey, and left eye/right hemisphere bias for controlling antipredatory and exploratory behaviours. However, these studies were independent of each other and therefore were not empirical demonstrations that the directions of visual lateralisation found in this species are present in the same individual, allowing the simultaneous performance of dual tasks. In our study the same Podarcis muralis individuals carried out one exploratory and one predatory test each. We allowed each lizard to move freely in a circular arena, with opaque walls, with either nothing or mealworm larvae in the centre. In the first case the test was an exploratory test, while in the second case it was a predatory one. The results indicated that lizards preferentially used the left eye to observe the environment--i.e., during exploration--and just tended to use the right eye during predation. Hence we conclude that in the Podarcis muralis lizard lateralisation is expressed in the same individual in opposite directions, in accordance with previous observations.

Lateralization in the escape behaviour of the common wall lizard (Podarcis muralis).

Lateralization in ectotherms is now as well studied as in endotherms. Bias in eye use seems widespread, particularly in several ectotherms, most of them having lateral eyes. Several studies evidenced that the right eye/left hemisphere is involved in predatory behaviour and food searching while the left eye/right hemisphere seems to control predator monitoring, making lateralized individuals able to carry out both tasks simultaneously. Starting from previous observations that demonstrated a right-eye/left-hemisphere preference for observing a prey in common wall lizards, Podarcis muralis, we investigated whether a visual lateralization in antipredatory behaviour is present too. In a first experiment, we induced lizards in a terrarium to escape from a simulated predator attacking from behind, recording the direction of the escape path in relation to the starting point. We found that the preferred escape direction of most lateralized individuals was to the right and there was also a strong rightward preference in escape direction as a whole. In a second experiment the lizards, again stimulated from behind, had to choose to run down either the right or the left arm of a semi-circular tunnel ("ram-horn" maze). The rightward preference in escape behaviour was confirmed in this experiment too. We conclude that the constant rightward escape could be due to a left-eye early perception of the threatening cue and to the possibility it gives of better monitoring of most of the terrarium surface. Moreover, we found a left bias in turning the head for monitoring the predatory stimulus during escape, supporting the hypothesis that such a preference is likely due to visual lateralization rather than to motor lateralization.