Fog caused distinct diversity of airborne bacterial communities enriched with pathogens over central Indo-Gangetic plain in India

Abstract

Fog causes enhancement of bacterial loading in the atmosphere. Current study represents the impact of occurrences of fog on the alteration of diversity of airborne bacteria and their network computed from metagenomic data of airborne samples collected at Arthauli (25.95°N, 85.10°E) situated at central Indo-Gangetic Plain (IGP) during 1-14 January 2021. A distinct bacterial diversity with a complex network is identified in foggy condition due to the enrichment of unique types of bacteria. Present investigation highlights a statistically significant enrichment of airborne pathogenic bacteria found in a unique ecosystem within air evolved due to the occurrences of fog over central IGP. In the foggy network, Cutibacterium, an opportunistic pathogen, is identified to be interacting maximum (21 edges) with other bacteria with statistically significant copresence relation, which are responsible for various infections for human beings. A 40-60% increase (p < 0.01) in the abundance of pathogenic bacteria for respiratory and skin diseases is noticed in fog period. Among the fog-enriched bacteria, Cutibacterium, Herbaspirillum, Paenibacillus, and Tsukamurella are examples of opportunistic bacteria causing various respiratory diseases, while Paenibacillus can even cause skin cancer and acute lymphoblastic leukemia.

Keywords: Airborne bacteria; Diversity; Fog; Indo-Gangetic plain; Pathogens.

Fig. 1

INSAT-3D satellite images captured occurrences of fog over IGP. The box (yellow) presents location of sampling site over central IGP. (a) Satellite image on January 10, 2021 at 0300 h showing sampling site free from fog occurred over North-western IGP (b) Photo taken from the rooftop of sampling site on January 10, 2021 present typical clear winter day. (c) Occurrences of fog over sampling site on January 12, 2021 at 0300 h depicting high intensity of fog spreading from west to east IGP, (d) Photo taken on January 12, 2021 at same location, indicating low visibility in a typical foggy day.

Fig. 2

Variation of (a) temperature and RH, and (b) WS and PBLH in pre-fog, fog and post-fog.

Fig. 3

Spatial distribution of RH, temperature (level 2 m; open contours) with wind speed and direction over the Indian subcontinent region on a typical winter day (10th January) retrieved from NCEP-NCAR Reanalysis data. Three-days air parcel back-trajectories on 10th (clear day) and 12th January (foggy day) using HySplit model at an initial height of 100 m at sampling site marked by a star (blue) are shown. A slower movement of wind on foggy day originated from west IGP has been noticed by back-trajectory analysis.

Fig. 4

(a) Boxes present Shannon's diversity index with standard deviations in pre-fog, fog and post fog conditions where each points present individual sample. (b) Beta diversity between three atmospheric conditions is represented as PCoA plot, where ellipse is observed for fog and post-fog conditions.

Fig. 5

Network analysis showing interactions among bacteria (green edges-copresence, red edges-mutual exclusion) in (a) pre-fog, (b) fog, and (c) post-fog.

Fig. 6

Average abundances of air-borne pathogenic bacteria targeting respiratory, skin and oral organs for human being in pre-fog, fog, and post-fog atmospheric conditions. The vertical lines present standard deviations. Two Asterisks (**) indicate significance level of p < 0.01.

Fig. 7

Average abundances of individual pathogenic bacterial genera in different atmospheric conditions. The horizontal lines represent standard deviations. Single (*) and double Asterisk (**) indicate significance level of p < 0.05, and p < 0.01, respectively for pre-fog and fog (green), fog & post-fog (blue), and overall (pink).