Investigation of bacteria diversity associated with dust in Khuzestan province

In recent years, dust storms have been increased health problems in Abadan and Khorramshahr. The purpose of this study was to investigate the origin of dust storms in Southwestern Iran from December 2018 to January 2020 using bio-aerosols and studied the effects of environmental parameters on bacterial concentrations by sampling soil of Hoor-Al-Azim and Shadegan wetlands as probable sources. A sampling of bio-aerosols and particulate matters was performed using Quick take30 sampler and environmental particle meter AEROCET531S, respectively. The images of the Moderate Resolution Imaging Spectroradiometer (MODIS) satellite and HYSPLIT model tracked the dust mass entering the air of Abadan and Khorramshahr. After the cultivation and isolation of bacteria from soil and air samples, their identification was conducted by the 16S rRNA gene sequencing method. Based on the results, Bacillus zhangzhouensis, Bacillus aerius, Bacillus subtilis, Paenibacillus, Bacillus mojavensis, Lysinibacillus macrolides were common bacteria identified in both the soil of Hoor-Al-Azim and Shadegan wetlands and the air of Abadan and Khorramshahr. Dust storms with domestic origins had more affect than foreign dust origin on bacteria concentration of Abadan and Khorramshahr. These results showed that dust storms could play an essential role in transmitting bacteria from their sources to remote locations. Bacillus bacteria (36genus) was known as the most common bacteria in Abadan and Khorramshahr air on dusty and non-dusty days due to their gram-positive (92%) and sporulating properties.

One of the phenomena that have caused air pollution in recent years and have had adverse environmental and health consequences is the dust storm. Iran is affected continuously by local dust systems due to its geographical location and location on arid and semi-arid belts. Most of Iran's dust activity comes from high-pressure intrusions from southern Iraq and northern Saudi Arabia. Drought, reduced rainfall, and relative humidity have caused to dry up some wetlands, lakes, and deserts in Iraq and Syria, which are strongly correlated with dust production areas. One of the essential functions of a wetland is to prevent dust storms. Vast volumes of dust from dry land and deserts carry biological agents at great distances. Dust storms increase the concentration of (PM 2.5, PM10) and opportunistic pathogens on a large scale, thus affecting the population and downstream ecosystems of the dust stream and increasing a wide range of diseases. Bio-aerosols are airborne particles containing bacteria, fungi, viruses, protozoa, algae, plant pollen and microorganisms that originate from natural and artificial sources. Their natural source; Soil, lakes, oceans, animals, humans (sneezing, coughing, and other activities), are plants and dust particles that absorb bio-aerosol on their surfaces. Several artificial sources that originate from bio-aerosols include wastewater treatment, fermentation processes, and agricultural activities that disperse the soil. Studies in Iran on bio-aerosols have been primarily on indoor environments and based on morphological methods. Few studies in outdoor environments, mainly wetlands, have used molecular approaches to study bio-aerosols. Our studies, for the first time, using molecular techniques show the similarity between the bacteria in the soil of Hoor-Al-Azim and Shadegan wetlands with the bacteria in the air of Abadan and Khorramshahr. A variety of approaches for dust storm monitoring have been proposed and evaluated. Remote sensing, compared with other procedures, is becoming one of the most popular methods to detect dust storms at large scales due to its ability of efficient global coverage. Sensors installed on satellites detect different types of Earth's surface radiation that are effective in monitoring, and identifying the origin of dust, obtaining the required parameters for dust modeling and obtaining quantitative dust-related relationships such as optical depth particle size. Therefore, in this study, remote sensing was used to determine the source of dust. Also, the HYSPLIT model was used to identify the origin and trace the entry of dust into the air of Abadan and Khorramshahr.

2.1 Detection of Abadan and Khorramshahr Air DustIn the present study, satellite information, Khuzestan Environment Department, and Abadan Meteorological Station were used to determine the dust days of Abadan and Khorramshahr. Daily Images of the Terra and Aqua satellites were downloaded from http://ladsweb.modaps.eosdis.nasa.gov/search and reviewed with classic ENVI software and MCTK plugin used for pre-processing (geometric correction, radiometric, atmospheric) images. 2-2. Sampling stations and sample collectionSampling of surface soil carried out in Hoor Al-Azim (31º33ʹ44ʺN, 47º39ʹ38ʺE) and Shadegan (30º38ʹ58ʺN, 48º39ʹ52ʺE) wetland randomly. The sampling sites were selected to measure airborne particulate matter, bacteria, moisture, temperature, and ultraviolet radiation under USEPA standards. According to these standards, the Abadan College of Medical Sciences (ACMS), Khorramshahr Fire Department (KFD), Khorramshahr Fisheries and Aquatic Office (KFAO), Farzanegan School Abadan (FSA) and Eight Station (ES) were selected as sampling sites for ten days.2.3. Morphological and microscopic identificationBacteria isolated from the surface soil of Hoor AL-Azim and Shadegan Wetlands were serially diluted. Samples collected from the air of the study area were incubated on the Nutrient agar medium for 24 to 72 h. Different colonies grew on the nutrient agar medium. Bacterial concentrations were also evaluated according to Colony (CFU/m3) and morphological characteristics. Gram staining was used for the microscopic study of the desired isolates.2.4. DNA ExtractionThe phenol/chloroform method was used as the DNA extraction method in this study.

3.1. Results of the MODIS Satellite ImagesAccording to the data obtained from satellite information, the General Department of Environment of Khuzestan Province and Abadan Meteorological Station dates of 2019/5/8, 2019/5/19, and 2019/6/13 were identified as dusty days. The results of dust detection by MODIS image showed that the BTD (23-31)>5.5 threshold had a high ability to detect dust, compared to other thresholds used. Therefore, the BTD index was capable of detecting dust, but varied from image to image due to differences in cloud properties, reflecting surface, changes in dust mass characteristics (height and mineral structure particle). The results of HYSPLIT model showed that the air masses originated from Syria and Iraq (on the day with the northern wind), Saudi Arabia (on the day with the southeastern wind), and Syria (on the day northwest wind). The results obtained from the present study showed that the images of MODIS satellite and HYSPLIT model can complement to each other and are very suitable to tracking the movement of dust mass entering the aquatic and terrestrial ecosystems and the bacteria transmitted with them.3.2 Comparison of sampling stationsThe results showed that the highest mean concentration 127.94 CFU/m3 of airborne bacteria was observed in (ACMS) station and lowest mean concentration 30.98 CFU/m3 of airborne bacteria was observed in (FSA) station. According to the result of ANOVA, there was a significant difference between the mean of stations (p-value <0.05). The significance level of ANOVA is less than 0.05 and indicates differences between groups. The results of T-test analysis showed that there was a significant difference between bacterial concentration in the (KFD) compared to the two (ES) and (ACMS) (p-value <0.05). The average (KFD) was significantly lower than the two groups of (ES) and (ACMS). The mean bacterial density in (KFAO) was significantly lower than the average bacterial concentration in the two stations of (ES) and (ACMS) (p-value<0.05). The mean bacterial concentration in (FSA) was significantly lower than the average bacterial concentration in the Eight station (ES) and (ACMS) (P<0.05). In summary, the results showed that the mean bacterial concentration in the two (ACMS) and (ES) was no difference, but was significantly higher than the mean of the other three stations. Several factors contributed to the increase of bacterial concentration in the (ACMS) Abadan College of Medical Sciences. The occurrence of local dust at the sampling time may be the most critical factor in increasing bacterial concentration at the station. Also, the (ACMS) is one of the educational sites, and due to its proximity to Abadan International Airport, it resulted in increased bacterial concentration at the station compared to other stations