The Microbiology of the Atmosphere

Abstract

Aerobiology is usually understood to be the study of passively airborne micro-organisms-of their identity, behaviour, movements, and survival.One characteristic, which it shares with many other population studies in biology, is that the ultimate relevant unit consists of the individual cell or small group of cells.Analysis at the molecular or sub-atomic level is irrelevant to our present purpose.Like geography, aerobiology is an agglutinative study, drawing information from many kinds of scientific research.Although it already has its patron saint, Pierre Miquel, and its martyr, Fred C. Meier, aerobiology is best regarded as an activity whose material will in due course be incorporated into the main body of bio- logical science-without, I hope, any necessity for splinter societies, journals, and international conferences.This book amplifies and extends a course of Intercollegiate Lectures given to botanical students in the University of London in 1956.The theme, which has occupied me for over fifteen years, is as follows.Trans- port through the atmosphere is the main dispersal route for such organic particles as the spores of many micro-organisms.How do the properties of the atmosphere, and the properties of these particles themselves, affect their dispersal?How do the particles get into the air?How far, and in what numbers, are they dispersed?By what processes do they become grounded, so that they can continue growth ?What is in the air, and how can we measure it ?What are the practical consequences of this process for the micro-organisms themselves, and for man, other animals, vegetation, and crops ?Although there are one or two other books on airborne microbes, this is the first to treat the subject as a world-wide phenomenon.It is, perhaps, inevitable that it should be attempted by a mycologist.Few other biologists find their material so dominated by the atmosphere, and no other micro- organisms have so thoroughly exploited the possibilities of aerial dispersal as the fungi.One of the fascinations of the subject is the impact of facets of its knowledge on such apparently diverse topics as artificial rain-making, allergy, smoke screens, effluent of nuclear power-stations, crop protection, icing of aircraft, air hygiene, and many other topics.This book treats of the development and principles of aerobiology rather than applications; yet the stimulus to nearly all aerobiological work comes from applied science.In this book the term 'microbe' is used freely when a general word is wanted; but, like the word 'spore', it has admittedly been stretched beyond its normal meaning.Airborne pollen of flowering plants must be Included and is safely covered by the term 'spore' (botanically : 'micro- spore') ; but are pollen grains and mushroom spores microbes ?There is no other commonly accepted word that covers quite what is meant by the word 'spore' as used here: 'propagule', 'disseminule', 'biota', 'diaspore'?We have isolated part of the continuum for study but find we are not well- equipped verbally for the task of dealing with it.The microbial population of the atmosphere is referred to here as the 'air-spora', using 'spora' as a word analagous to 'flora' and 'fauna'.Botanical nomenclature has presented some difficulties: authorities have not been given for specific names, and the names used by other authors have usually been quoted as given in the original papers-without necessarily attempting to guess what was meant, or following the nomenclature fashionable in i960.I have converted other workers' numerical data to the metric system, and temperature to the Centigrade scale, to aid comparison, and have moreover assessed spore concentrations on the uniform basis of number per cubic metre.Frequently, in making general statements, I have omitted safeguarding, but tedious, escape clauses: this has been done to spare the reader who will understand that biological generalizations aboun-d in exceptions and complexities.Interpretations in this book are mostly my own responsibility, but I am