A rapid photothermal bacterial inactivation technique has been developed by irradiating near-infrared (NIR) light onto bacterial cells (Escherichia coli, Bacillus subtilis, Exiguobacterium sp. AT1B) deposited on surfaces coated with a dense, random array of nanoporous gold disks (NPGDs). With the use of cell viability tests and SEM imaging results, the complete inactivation of the pathogenic and heat-resistant bacterial model strains is confirmed within ~25 s of irradiation of the NPGD substrate. In addition to irradiation control experiments to prove the efficacy of the bacterial inactivation, thermographic imaging showed an immediate averaged temperature rise above 200 °C within the irradiation spot of the NPGD substrate. The light-gated photothermal effects on the NPGD substrate offers potential applications for antimicrobial and nanotherapeutic devices due to strong light absorption in the tissue optical window, i.e., the NIR wavelengths, and robust morphological structure that can withstand high instantaneous thermal shocks.

No abstract

No abstract

The present study investigates the strain Kosakonia sp. ICB117, an endophytic, N 2 -fixing bacterium that belongs to a genus recently described. The bacteria were isolated from sugarcane stalks (Saccharum sp. variety SP791011) and inoculated into other sugarcane plants of the same variety. The effect of inoculation on sugarcane growth was then studied in the presence or absence of nitrate supplementation (10 mM). The following plant growth parameters were analyzed: biomass, plant height and number of leaves. Furthermore, CO 2 assimilation and the C and N content of plants were also determined, as was the size of the endophytic bacteria population resulting from the inoculation. The findings showed that inoculation with bacteria (both with or without additional nitrate) led to an increase of plant biomass, CO 2 assimilation, total C and N in the roots, and the number of leaves. In addition, the polyamine putrescine and indole-3-acetic acid were actively released by the bacterium in in vitro assays and might be released in internal plant tissues as well, resulting in plant growth promotion. In conclusion, inoculation of sugarcane with Kosakonia sp. ICB117 increased the efficiency of the plant's metabolism.

In the present study, we take advantage of the high thermal conductivity of graphene nanomaterials to develop a filter that can be easily cleaned via laser irradiation after biofouling occurs. In this investigation, the intensity of the laser beam and the amount of graphene used for membrane coating were investigated with Bacillus subtilis to achieve the most efficient removal of biofoulants. Thermographic measurements of glass microfiber filters coated with 500 μg of graphene showed an increase in temperature of about 328 ± 9 °C in about 6 s when the filters were irradiated with a 21.6 W/cm −2 laser intensity, which allowed successful removal of biofoulants. The thermal cleaning was effective for at least four filtrations without impacting the subsequent microbial removals, which were of ∼5 log for each filtration step followed by laser irradiation. Additionally, the permeability of the coated filters only dropped from 17.8 to 15.9 L/m 2 s after the laser cleaning procedure. The cleaning procedure was validated by using bayou water with a complex composition of biofoulants. Graphene-coated membranes coupled with laser irradiation afford a very fast and nonhazardous approach to clean biofoulants on graphene-coated membranes.