Exploratory Study On Identification Of Bioaerosols By Mass Spectrometry

Bioaerosols are one of the important sources of pathogenic microorganisms,endotoxins and other allergens that invade the body through the respiratory tract and pose a potential hazard to human health.Infectious aerosols,especially human-derived pathogenic microbial aerosols,are prone to large-scale infectious diseases.The rapid detection of bioaerosol is a hot topic at present.The main methods for identifying bioaerosol are classified into online identification and off-line identification.Off-line identification methods include traditional microscopic observation combined with physiological and biochemical test identification,16 S rRNA sequencing and identification;online identification technology includes ultraviolet aerosol particle size analyzer based on fluorescent aerodynamic particle size meter principle and broadband integrated bio-aerosol sensor.However,due to the long time-consuming,complicated operation and high cost of the offline identification method,the online identification technology cannot detect the bio-aerosol without fluorescence characteristics,and is susceptible to external environment interference.The mass spectrometry technology is gradually used for off-line and online identification of bioaerosols.Such as Single Particle Aerosol Mass Spectrometry(SPAMS)and Matrix-Assisted Laser Desorption/Ionization Time of Flight Mass Spectrometry(MALDI-TOF MS).Our group has been engaged in the research of mass spectrometry for a long time,and independently developed SPAMS and MALDI-TOF MS.The purpose of this paper is to explore the feasibility of using MALDI-TOF MS and SPAMS to rapidly identify bioaerosols.The paper selected a canteen with dense population,which is relatively suitable to be a sampling site.The large-flow bioaerosol sampler was used to collect airborne bacteria.Finally 98 strains of bacteria grown on LB solid medium and 92 strains of bacteria grown in LB liquid medium were obtained and used for subsequent mass spectrometry analysis.98 strains of LB solid medium and 92 strains of LB liquid medium were identified by home-made MALDI-TOF MS.In order to judge the identification rate of the identification better,all bacteria were identified by 16 S rRNA and analyzed by commercial MALDI-TOF MS.Comparing the results of 16 S rRNA with MALDI-TOF MS,the identification rate of MALDI-TOF MS on genus and species level reach 89% and 74%,which is higher than the genus and species level identification rate obtained on two commercial mass spectrometers.(77%,59%,and 62%,58%,respectively).This is due to the database of home-made MALDI-TOF MS.It also shows that the home-made MALDI-TOF MS can be used to identify bioaerosols.In addition,the results of 16 S rRNA sequencing of some strains were inconsistent with those of MALDI-TOF MS.The analysis of MALDI-TOF MS spectra showed that the identification results of 16 S rRNA sequencing may be inaccurate,and subsequent attempts to identify again using whole genome sequencing technology to verify the guess.Thirteen different types of bioaerosols were analyzed using self-developed SPAMS.Analysis of the spectrum of these 13 kinds of bacteria shows that the characteristic peaks of the active bioaerosols are significantly different from those of other types of particles in the atmosphere,so these characteristic peaks can be used as the identification peaks of bioaerosols in the atmosphere.The positive ion spectrum is mainly composed of fragment ion peaks of amino acids such as glycine,proline,valine,isoleucine and trimethylglycine,including m/z=30,59,70,72,74,81.,84,86,88,110,120,the negative ion spectrum usually shows m/z =-26,-42,-79,-97 ion peaks,in addition to the unique negative ion characteristic peak m / z =-159 and-200 has not been reported in other papers before,and may be used as a unique characteristic peak of bioaerosols.The results show that SPAMS can be used as an effective means to quickly identify active bacterial aerosols online.However,there is no significant difference in the type of single particle spectrum of different species of bacteria,and it is difficult to identify biological bacteria at the genus and species level by the characteristic ion peaks of existing SPAMS.In the future,the ability to identify single-particle bacteria can be considered from two-step laser ionization and introduction of substrates.