Bioaerosol charge information is of vital importance for their electrostatic collection. Here, electrostatic means and molecular tools were applied to studying bioaerosol charge dynamics. Positively or negatively charged bioaerosols were collected using an electrostatic sampler operated with a field strength of 1.1 kV cm 1 at a flow rate of 3 L min 1 for 40 min. Those with fewer or no charges bypassing the sampler were also collected using a filter at the downstream of the electrostatic sampler in one environment. The experiments were independently conducted three times in three different environments. The collected bacterial aerosols were cultured directly on agar plates at 26°C, and the colony forming units (CFU) were manually counted. In addition, the CFUs were washed off from the agar plates, and further subjected to polymerase chain reaction (PCR) and denaturing gradient gel electrophoresis (DGGE) for culturable diversity analysis. The results revealed remarkable differences in positively and negatively charged culturable bacterial aerosol concentration and diversity among the studied environments. In the office environment, negatively charged culturable bacterial aerosols appeared to dominate (P = 0.0489), while in outdoor and hotel environments both polarities had similar concentration levels (P = 0.078, P = 0.88, respectively). DGGE patterns for positively charged culturable bacterial aerosols were shown strikingly different from those of negatively charged regardless of the sampling environments. In addition, for each of the environments positively charged culturable bacterial aerosols collected were found to have more band pattern similarity with those positively charged for respective regions of agar plates than those negatively charged, and vice versa. The information developed here is useful for developing efficient electrostatic sampling protocols for bioaerosols.
Nanoscale zero-valent iron(nZVI)particles are increasingly being investigated in removing aqueous contaminants.Here,we have demonstrated its inactivation and magnetic removal of bacteria and endotoxins from environmental wastewater samples.Varying dosages(10–1,000 lL)of 0–6 days aged nZVI with a concentration of 5 mg/mL for 2 mL wastewater samples were tested,and relevant removal efficiencies were determined using culturing method for bacteria and limulus amebocyte lysate(LAL)for endotoxins.The supernatants of wastewater samples after reacting with nZVI and subsequent magnetic separations were subjected to spectroscopic,qPCR and DGGE analysis.Overall,high magnetic bacterial removal efficiencies were observed up to 3–4 logs for 1 mL nZVI,while the removal efficiencies decreased sharply down to0.5 log for 10 lL nZVI.qPCR and DGGE results revealed that higher dosages of nZVI caused severe bacterial cell membrane ruptures,releasing significant amounts of DNA up to 107–108gene copies/mL when 1 mL nZVI was used.Richer DGGE patterns were observed for higher nZVI dosages.In addition,regardless of the dosages(10–1,000 lL)we have observed more than 90%removal of endotoxins from the wastewater samples.The described technology has great promise to be used as a point-of-use water purification solution for various purposes.
Infectious diseases cause tremendous costs of both human and economy annually.Previously,we have studied the bacterial,fungal,and allergen aerosol inactivation by direct microwave irradiation.Here,we further investigated its effects on airborne viruses.MS2 coliphage used as a human model virus was aerosolized and exposed to the direct microwave irradiation for*2 min at three different power levels(700,385,and 119 W).In addition to the survival rate,the viral genes before and after the microwave treatments were also examined using PCR and gel electrophoresis.Direct exposure of airborne MS2viruses to the microwave irradiation at 700 W for less than2 min was shown to result in more than 90%inactivation efficiency,about 65%at medium power level(385 W),and 50%at the lowest level(119 W).The aerosol inactivation rate followed a linear relationship with the microwave exposure time(R2=0.9889).Scanning electron images revealed visible damages to the viral surface after the exposure.Damages were also observed to the viral RNA genes coding for coat proteins,among which the A protein gene was completely destroyed.This study demonstrated that even without the filtration the direct microwave irradiation could also achieve rapid inactivation of viral aerosols.The information obtained can provide useful guidance on the development of microwave-based viral threat mitigation solutions in a closed or semi-closed space.
