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Abstract:
Coughing, sneezing, talking, bed-making, turning pages of books, etc. all generate microbial aerosols which are carried and dispersed by air movements. Inhalation of these particles may cause allergic responses but whether or not infectious disease ensues depends in part on the viability and infectivity of the inhaled microbes and their landing sites. Desiccation is experienced by all airborne microbes; gram-negative bacteria and lipid-containing viruses demonstrate phase changes in their outer phospholipid bilayer membranes owing to concomitant changes in water content and/or temperature. These changes most likely lead to cross-linking reactions of associated protein moieties principally at mid to high relative humidity (RH). For lipid-free viruses these reactions of their surface protein moieties occur most rapidly at low RH. Radiation, oxygen, ozone and its reaction products and various pollutants also decrease viability and infectivity through chemical, physical and biological modification to phospholipid, protein and nucleic acid moieties. The extent of damage and the degree of repair together with the efficacy of host defence mechanisms largely controls whether the causative microbes take hold and spread disease via the airborne route. At least indoors, where desiccation is the predominant stress, the general reversibility of membrane-phase changes by vapour-phase rehydration when coupled with efficacious microbial enzymatic repair mechanisms under genetic control, virtually ensures the spread of disease by the aerobiological pathway.
Insights
Microbial aerosols spread disease indoors. While environmental stresses like desiccation damage airborne microbes, their repair mechanisms and rehydration capabilities ensure disease transmission via the aerobiological pathway.
Area of Science:
- Aerobiology
- Microbiology
- Environmental Health
Background:
- Microbial aerosols are generated by common activities and dispersed by air.
- Inhaled microbes can cause allergic responses or infectious diseases.
- Microbial viability and infectivity depend on environmental factors and host defenses.
Purpose of the Study:
- To investigate the factors influencing microbial viability and infectivity in airborne particles.
- To understand the mechanisms by which microbes survive and cause disease via the aerobiological route.
Main Methods:
- Analysis of microbial responses to environmental stresses such as desiccation, radiation, oxygen, ozone, and pollutants.
- Examination of phase changes in microbial membranes (phospholipid bilayers) and protein moieties at varying relative humidity (RH).
- Assessment of microbial damage, repair mechanisms, and host defense interactions.
Main Results:
- Desiccation is a primary stress for airborne microbes indoors.
- Gram-negative bacteria and lipid-enveloped viruses undergo membrane phase changes affecting protein cross-linking, particularly at mid to high RH.
- Lipid-free viruses experience rapid surface protein reactions at low RH.
- Environmental factors like radiation and pollutants cause chemical, physical, and biological damage to microbial components.
- Microbial repair mechanisms, especially enzymatic repair under genetic control, can counteract damage.
- Reversibility of membrane changes through rehydration is crucial for survival.
Conclusions:
- The interplay between microbial damage and repair, alongside host defenses, dictates airborne disease transmission.
- Indoor desiccation is a key stress, but microbial repair and rehydration mechanisms ensure the persistence of pathogens.
- The aerobiological pathway remains a significant route for infectious disease spread due to microbial adaptability.