Nanoscale Zero-Valent Iron Modified by Bentonite with Enhanced Cr(VI) Removal Efficiency, Improved Mobility, and Reduced Toxicity

The aggregation of nanoscale zero-valent iron (nZVI) particles and their limited transport ability in environmental media hinder their application in environmental remediation. In this study, the Cr(VI) removal efficiency, transport performance, and toxicity of nZVI and bentonite-modified nZVI (B-nZVI) were investigated. Compared with nZVI, B-nZVI improved the removal efficiency of Cr(VI) by 10%, and also significantly increased the transport in quartz sand and soil. Increasing the flow rate can enhance the transport of nZVI and B-nZVI in the quartz sand columns. The transport of the two materials in different soils was negatively correlated with the clay composition. Besides, modification of nZVI by bentonite could reduce toxicity to luminous bacteria (Photobacterium phosphereum T3) and ryegrass (Lolium perenne L.). Compared with Fe-EDTA, the transfer factors of nZVI and B-nZVI were 65.0% and 66.4% lower, respectively. This indicated that although iron nanoparticles accumulated in the roots of ryegrass, they were difficult to be transported to the shoots. The results of this study indicate that B-nZVI has a strong application potential in in situ environmental remediation.

Modeling the underlying environmental factors of milky sea case and luminous bacteria presence in Java Southern Sea in 2019

The milky sea is one of the unique natural phenomena caused by the presence of luminous Vibrio bacteria in marine ecosystems. Recently a milky sea has been reported frequently included in the Java Southern Sea. Simultaneously, numerous remote sensing based approaches have been developed to detect the presence of luminous bacteria and the milky sea. Despite this state of the art, the information of detrimental factors of the marine bioluminescence was still limited. Then this research aims to model the underlying environmental factors causing the milky sea and luminous bacteria presence in the Java Southern Sea in 2019. The remote sensing assessment for the period of July 29-August 6, 2019 shows that the magnitude of bioluminescence measured in radiance was having a maximum value of 255 nanoW/cm2/sr and an average of 107 nanoW/cm2/sr/day (95%CI: 71.9 to 142 nanoW/cm2/sr/day). The milky sea size increased and reached its peak with a size of 44,124 km2 and then declined. The average milky sea size was 37,942 km2 (95% CI: 33,400 to 42,500 km2) and increased with average rate of 16.01% (95%CI: 5.41% to 26.66%). While Akaike Information Criterion (AIC) indicates that the best model to infer the relationship of bacterial bioluminescence with its environmental factors contained Chlorophyll a followed by sea surface temperature factors with AICc values of 101.16 (AICweight: 0.50) and 101.95 (AICweight: 0.34). This indicates that low temperature and high plankton cells is the limiting factors of the bacterial bioluminescence.

Effect of metal concentration on growth and luminescence of luminous bacteria strains isolated from golfo de Nicoya, Costa Rica

Luminescence in bacteria is catalyzed by luciferase. When these microorganisms are exposed to toxic substances, the bioluminescent enzyme system can be inhibited. The objective of this study was to analyze the potential that these microorganisms offer as native bioindicators of coastal marine pollution. The dynamics of luminescence intensity by visual classification and the effect of metal concentration on the growth and luminescence of 25 strains of luminescent bacteria, isolated during 2016 from seawater samples from the gulf of Nicoya, Costa Rica, was evaluated by the disk diffusion method. The sensitivity of each strain to different concentrations (0.1, 0.5 and 1 mg mL-1) of Cd, Cu, Cr, Pb and Zn was determined by its bioluminescent phenotype. In susceptible strains, a range of metal concentrations less than the growth inhibitory concentration affected the expression of luminescence. Strains with intense luminescence and defined zones of luminescence inhibition were considered to have greater potential as native bioindicators for monitoring environmental toxicity. More studies are required to determine the minimum concentrations that inhibit growth and luminescence with respect to the tested metals and other potentially toxic substances for the coastal marine ecosystems of Costa Rica.

Museum Genomics Illuminate the High Specificity of a Bioluminescent Symbiosis for a Genus of Reef Fish

Symbiotic relationships between bioluminescent bacteria and fishes have evolved multiple times across hundreds of fish taxa, but relatively little is known about the specificity of these associations and how stable they are over host generations. This study describes the degree of specificity of a bioluminescent symbiosis between cardinalfishes in the genus Siphamia and luminous bacteria in the Vibrio family. Primarily using museum specimens, we investigated the codivergence of host and symbiont and test for patterns of divergence that correlate with both biogeography and time. Contrary to expectations, we determined that the light organ symbionts of all 14 Siphamia species examined belong to one genetic clade of Photobacterium mandapamensis (Clade II), indicating that the association is highly specific and conserved throughout the host genus. Thus, we did not find evidence of codivergence among hosts and symbionts. We did observe that symbionts hosted by individuals sampled from colder water regions were more divergent, containing more than three times as many single nucleotide polymorphisms than the rest of the symbionts examined. Overall, our findings indicate that the symbiosis between Siphamia fishes and P. mandapamensis Clade II has been highly conserved across host taxa and over a broad geographic range despite the facultative nature of the bacterial symbiont. We also present a new approach to simultaneously recover genetic information from a bacterial symbiont and its vertebrate host from formalin-fixed specimens, enhancing the utility of museum collections.

Museum genomics illuminate the high specificity of a bioluminescent symbiosis across a genus of reef fish

Symbiotic relationships between bioluminescent bacteria and fishes have evolved multiple times across hundreds of fish taxa, but relatively little is known about the specificity of these associations and how conserved they have been through time. This study describes the degree of specificity of a bioluminescent symbiosis between cardinalfishes in the genus Siphamia and luminous bacteria in the Vibrio family. Primarily using museum specimens, we investigate the co-divergence of host and symbiont and test for patterns of divergence that correlate with both biogeography and time. Contrary to expectations, we determined that the light organ symbionts of all 14 Siphamia species examined belong to one genetic clade of Photobacterium mandapamensis (Clade II), indicating that the association is highly specific and conserved across the host genus. Thus, we did not find evidence of codivergence among hosts and symbionts. We did observe that symbionts hosted by individuals sampled from colder water regions were more divergent, containing more than three times as many single nucleotide polymorphisms than the rest of the symbionts examined. Overall our findings indicate that the symbiosis between Siphamia fishes and P. mandapamensis Clade II has been highly conserved across a broad geographic range and through time despite the facultative nature of the bacterial symbiont. These results suggest that this bioluminescent symbiosis could have played a key role in the evolution of the host genus and that there are conserved mechanisms regulating its specificity that have yet to be defined.

Humic Substances Mitigate the Impact of Tritium on Luminous Marine Bacteria. Involvement of Reactive Oxygen Species

The paper studies the combined effects of beta-emitting radionuclide tritium and Humic Substances (HS) on the marine unicellular microorganism—luminous bacteria—under conditions of low-dose radiation exposures (<0.04 Gy). Tritium was used as a component of tritiated water. Bacterial luminescence intensity was considered as a tested physiological parameter. The bioluminescence response of the marine bacteria to tritium corresponded to the “hormesis” model: it included stages of bioluminescence inhibition and activation, as well as the absence of the effect. HS were shown to decrease the inhibition and activation effects of tritium, similar to those of americium-241, alpha-emitting radionuclide, studied earlier. Correlations between the bioluminescence intensity and the content of Reactive Oxygen Species (ROS) were found in the radioactive bacterial suspensions. The results demonstrate an important role of HS in natural processes in the regions of low radioactive contamination: HS can mitigate radiotoxic effects and adaptive response of microorganisms to low-dose radioactive exposures. The involvement of ROS in these processes was demonstrated.

Assessment of the applicability of primarily identified natural luminescent bacteria, isolated from the azov and the black seas, to determine the antimicrobial activity of antibiotics

Five isolates of luminous bacteria from aquatic organisms of the Azov and the Black Seas were isolated. The study of morphological, cultural, physiological and biochemical properties showed that isolates M1 and M4 were the representatives of the species harveyi, and isolates Fb, Sh1, and B were the representatives of the species P. leiognathi. It was found that the strain P. leiognathi Sh1 was the most sensitive to zinc sulfate when studying its effect on allocated luminescent bacteria. The effective concentration that reduced the bioluminescent index (BLI) by 50% (EC50) for zinc sulfate, when exposed to the test strain, was 4,0 0,1 g/ml. Experimental data allowed to consider the strain P. leiognathi Sh1 to be the test-object for determining the antimicrobial activity of benzylpenicillin, gentamicin, streptomycin, tetracycline and ceftriaxone. The results of evaluating the effect of antibiotics on the test object, revealed that after 15 minutes of incubation, the BLI values decreased by 50% only in samples containing benzylpenicillin, gentamicin, and tetracycline. Their EC50 were 500.0, 283.0 and 28.5 g/ml respectively. It was found that the exposure of test-strain to all antibacterial agents demonstrated resulted in decrease in BLI by 100% as compared to the control values. Strain P. leiognathi Sh1 can be used as a test-object for determining the antimicrobial activity of antibiotics.