Applicability of LIVE/DEAD BacLight Stain with Glutaraldehyde Fixation for the Measurement of Bacterial Cell Concentration and Viability in the Air

Zhang

2016

JGR Atmospheres

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Airborne bacteria are a major group of bioaerosols, but their temporal and spatial variations in the atmosphere are poorly understood due to a lack of accurate information at an appropriate temporal resolution. In this study, we quantified the concentration and viability of airborne bacteria at a seaside site on the southwestern coast of Japan in spring to investigate their association with synoptic weather, which was governed alternately by cyclones and anticyclones moving in the middle‐latitude westerly flow. The concentration of bacteria, on the order of 105–106 cells m−3, showed a small amplitude of variation, while the viability significantly differed in the range of 23–96% under different weather conditions. Cyclones transported bacteria from the Asian continent in their postfrontal air. Compared to bacteria under other weather conditions, the bacteria in postfrontal air had a large concentration, a low viability, and a close correlation with coarse aerosol particles. In contrast, bacterial concentration and viability in prefrontal air varied over small ranges, and no correlation between bacteria and aerosol particle number concentration was observed. During anticyclones, although bacterial concentration was similar to that in prefrontal air, bacterial viability was high, and the concentration had pulse increases of approximately 2 times the usual level when the wind changed to land/sea breezes. The increases were attributed to the accumulation of bacteria in stagnant air due to local sources. These results show the following two distinct patterns of bacterial concentration and viability at the seaside location of this study: (1) during postfrontal long‐distance dust plume transport related to a cyclone approaching from the Asian continent, the bacterial concentration is correlated with the coarse aerosol particle number concentration and the bacterial viability is low, and (2) pulse increases of viable bacteria are observed at anticyclone conditions corresponding to local sources and land‐sea breeze conditions.

Section: Methodsmentioning

confidence: 99%

Concentration of bacterial aerosols in response to synoptic weather and land‐sea breeze at a seaside site downwind of the Asian continent

Zhang

2016

JGR Atmospheres

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“…Glutaraldehyde was used to minimize cell destruction during the experiment and to prevent fluorescent bleaching of bacterial cells under exposure to excitation rays (450–490 nm). Based on statistical analyses, the glutaraldehyde fixation could increase the detection accuracy to some extent (Hu, Murata, & Zhang, ; Murata & Zhang, ). The stain labeled the bacterial cells differentially based on the integrity of the cell membranes: cells with injured membranes were stained red, and those with intact membranes were stained green.…”

Section: Methodsmentioning

confidence: 99%

Concentration and Viability of Airborne Bacteria Over the Kuroshio Extension Region in the Northwestern Pacific Ocean: Data From Three Cruises

Fukuyama

et al. 2017

JGR Atmospheres

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Airborne bacteria have been shown to act as condensation and ice nuclei in mixed‐phase clouds and are consequently hypothesized to have significant effects on atmospheric processes and even the global climate. However, few data are available regarding their concentration and variation in the air over the open ocean. Aerosol samples were collected during three cruises in the early summers of 2013, 2014, and 2016 over the Kuroshio Extension region of the northwest Pacific Ocean. The concentrations of viable and nonviable bacterial cells in the marine surface air were quantified using epifluorescence enumeration with the LIVE/DEAD BacLight stain. The concentrations of total bacteria varied between 1.0 × 104 and 2.5 × 105 cells m−3 and averaged 5.2 × 104, 1.0 × 105, and 7.5 × 104 cells m−3 in the three respective cruises. The viabilities, i.e., the ratios of the concentration of viable bacterial cells to that of total bacterial cells, ranged from 80% to 100% (average 93%), and the respective means were 93%, 89%, and 96% in the cruises. The total bacterial concentration had a close correlation with the wind speed near the sea surface, and the bacterial viability correlated negatively with the air temperature, sea surface temperature, and concentration of coarse particles (size > 1 μm). The deposition and sea spray fluxes of bacteria were roughly estimated as hundreds of cells m−2 s−1 on average. The limited data on bacterial concentration and viability from the three cruises indicate the rapid air‐sea exchange of bacteria over the Kuroshio Extension region of the northwest Pacific Ocean.

“…They confirmed that the results on the total counts of bacterial cells by LIVE/DEAD Bacterial Viability Kit staining were consistent with those by DAPI staining. They further found that the detection efficiency could be increased a little by using the glutaraldehyde fixation as mentioned by Murata and Zhang (2013). However, if the amount of precipitation is small (less than 1.2 mm in their studies), the uncertainties might be very large, and the epifluorescence microscopy enumeration method using the LIVE/DEAD BacLight stain and the glutaraldehyde fixation is not able to ensure the quality of the measurements of bacterial abundance in the rainwater.…”

Section: Concentration and Viability In Rainwatermentioning

confidence: 99%

“…The applicability of the stain to airborne bacteria was carefully examined by Murata and Zhang (2013), with DAPI stain as the control of total cell counts. In contrast to blue color of bacterial cells stained by DAPI, viable and non-viable bacterial cells stained by the LIVE/DEAD BacLight stain are present in green and red colors, respectively.…”

Section: Live/dead Baclight Stain and Its Applicability To Airborne Bmentioning

confidence: 99%

Concentration and Viability of Bacterial Aerosols Associated with Weather in Asian Continental Outflow: Current Understanding

Zhang

et al. 2017

Aerosol Sci Eng

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Constituting a major fraction of bioaerosols, airborne bacteria take part in various atmospheric processes. Studies have suggested that airborne bacteria likely play an important role in cloud formation and consequently influence the solar radiation transfer and chemical conversions in the atmosphere, in addition to acting as links between geographically isolated microbial communities. However, how bacteria are dispersed in airflows remains poorly understood, because of the lack of reliable methods to describe the variations of airborne bacteria responding to changes in weather. We developed a simple method based on epifluorescence enumeration using LIVE/DEAD BacLight stain, by which we measured the concentrations of viable and non-viable bacterial cells in open air at a time resolution of 1 h or less. Although this method is laborintensive, laboratory experiments and applications in field observations have demonstrated its reliability and effectiveness in studies on the correlation between airborne bacteria and Asian dust, the dependence of airborne bacteria on regional and synoptic weather, and the presence of bacteria in rainwater. In this short review, we briefly introduce the method, report the progress with its application to bacteria in Asian continental outflow, address the significance of meteorological factors in controlling the variation of airborne bacteria, and give perspectives on future studies in terms of the dynamics of bacterial aerosols in the atmosphere.