ITS and 16S rRNA Gene Revealed Multitudinous Microbial Contaminations of Residential Air Conditioning Filters in Megacity Shanghai,China

Air conditioning is a crucial participant in indoor air circulation and harmful microorganism transmission.To elucidate microbial contamination in air conditioning systems,bacteria,fungi,and pollens in residential air conditioning(AC)filters in Shanghai were revealed.The concentrations of fungal ITS(1,972,037±5,025,505 copies/cm^(2))in most filter samples were considerably higher than the 16S rRNA gene(21,587±21,461 copies/cm^(2)).The multitudinous bacteria determined a higher richness,whereas the trend was not in line with fungi,owing to Aspergillus flourishing,with an average of 43.75%.Numerous bacteria that may often be prevalent in human skin,mucous membranes,and intestines,such as Enhydrobacter,Micrococcus,Staphylococcus,Streptococcus,and Haemophilus,were also discovered in AC filters.The pollens were affiliated with Streptophyta at phylum,and Humulus was the most abundant genus(mean value 67.84%),raising the possibility of allergic responses.This study provides a better understanding of the microbial characteristics of AC filters,enables more rational approaches for microbe contaminant control,and ultimately improves human health in megacities.