History of Microbial Ecology

HISTORY OF MICROBIAL ECOLOGY What is Microbial ecology? Ecology – Definition? Greek “oikos” = household “logos” = law ‘Law of the household” What laws, what household? Describes relationships between living (biotic) and nonliving (abiotic) systems. Microbial ecology describes this relationship among: Microorganisms Microorganisms and their environment Microorganisms and macroorganisms What are microorganisms? Are these microorganisms? Viruses Bacteria Protozoa Algae Fungi Development of microbial ecology Development of microbial ecology was based in studies of environmental quality Microorganisms were recognized as important and remain popular today Disease and public health Degradation Biotechnology Food safety Agriculture Etc. Microbial Ecology, History of Microbial Ecology Sigler 1 Advances in the study of microorganisms were closely coupled with methodological advances. Most advances have been made in the past 35 years Culture media and techniques Nucleic acid technology Decreased costs of sensitive and specific assays Technology was much more primitive during the early years of microbiology. First magnifying lenses were constructed in 1267 by Roger Bacon. Useful to enlarge detail on small organisms, but not useful for microbiology In the 1600s, Zacharius Janssen, a spectacle maker found that two lenses were better than one – the first microscope. The microscope was perfected in the 1620s by Galileo Galilei. In 1660s, Robert Hooke, an English philosopher and inventor, first used the microscope to look at cork, plant infecting fungi, and mold. Also developed the universal joint, respirator Primarily a tinkerer Microbial Ecology, History of Microbial Ecology Sigler 2 1670s - Microbes first described by Anton van Leeuwenhoek. Expanded the field of microbiology by improving the microscope and chronicling his observations. Microbes in wine and beer (important later) Impact of pepper on microbes (environmental impact) Asked Hooke to confirm findings (review) Microbes in rainwater (habitat study) Diversity was fascinating to van Leuwenhoek, likely protozoa. These represented the initial microbial ecology studies Revolutionary for the 1600s van Leeuwenhoek communicated many of his results including the first discussion of bacteria in 1683. Little advancement in microbiology until the mid 1800s, why? Microbial Ecology, History of Microbial Ecology Sigler 3 Louis Pasteur In the 1850s, Louis Pasteur showed that microbes might be agents of disease. This spurred massive re-interest in microbes. Technology advanced accordingly Pasteur answered the question of why French wines were turning sour. Prevailing theory: fermentation was purely a chemical process with no input by living organisms. Pasteur’s evidence against this… Pasteur showed tiny organisms in the wine (what were they?) Sour wines contained populations of the bacteria described by van Leeuwenhoek. When yeast cells were removed through heating, no fermentation would take place. When yeast cells were added back, fermentation would occur. Pasteur brought microbes into the public health arena Since the role of microbes in public health was becoming important, two questions were at the scientific forefront: 1. Does spontaneous generation occur? 2. What is the nature of contagious disease? Spontaneous generation (Pasteur) Where do microbes that spoil food come from? Two prominent theories: “Seeds” or germs from the air (not widely accepted). Arose spontaneously (surprisingly, widely accepted). Pasteur provided evidence against spontaneous generation. Filtered air and trapped organisms similar to those growing in rotten food Microbial Ecology, History of Microbial Ecology Sigler 4 Therefore, if food was treated to render microbes inactive, then it should not putrefy. So Pasteur heated the food to kill microbes…no putrification. Critics said that the removal of oxygen during the heating, not the heat treatment, limited microbial growth. Pasteur performed experiments with a “swan-necked flask” Microbial Ecology, History of Microbial Ecology Sigler 5 Take Home Message – Pasteur is responsible for the beginnings of food safety and the evidence that microbes might be agents of communicable diseases. Nature of Infectious Disease (Robert Koch) In the 1500s it was known that disease involved transmission of some vector between people. Even after the discovery of microorganisms, there was no proof that implicated them in causing disease. In 1875, Robert Koch developed the “germ theory of disease”. Worked with anthrax (Bacillus anthracis), which, at the time, was associated with a blood infection in cattle and sheep. But was it the cause or the result of the disease? Koch used two steps of analysis of mice to answer the question. First, Koch drew blood from a diseased mouse and injected it into a healthy mouse – mouse became diseased. This was repeated several times to show that B. anthracis caused the disease. Microbial Ecology, History of Microbial Ecology Sigler 6 Microscopy showed that B. anthracis was always present in diseased blood. Second, B. anthracis cultured from the mouse retained it’s pathogenicity. These findings led to the development of Koch’s Postulates. Used to relate a single microbe to a single disease. Koch’s experiments illustrated the importance of laboratory culture and methods to isolate microbes from a complex mixture. Take Home Message: Specific microbes have specific impacts. Microbial Ecology, History of Microbial Ecology Sigler 7 In the 1900s there were two prominent environmental microbiologists: Martinus Beijerinck – developed enrichment culture Original isolation strategies involved “chance” growth of the organism of interest on non-selective media. Biejerinck’s strategy involved the use of specific media that dictated what would grow. Isolated many of the first cultures of water and soil microorganisms. Sergei Winogradsky Mainly interested in soil organisms and the processes they mediate. Showed that nitrification (NH4 process dependent on bacteria. Why is this process important? Winogradsky column NO3) was a Microbial Ecology, History of Microbial Ecology Sigler 8 1950s – After WWII there were great advances in microbial research, mostly as a result of population growth, which: increased public health awareness (communicable disease) environmental deterioration (pollution) 1962 – “Silent Spring” published and exposed the hazards of DDT DDT was an insecticide that possessed non-target impacts Harmless insects Birds The book changed mans view of the sustainability of the environment and also stimulated research in biodegradation of xenobiotics. 1970s - Advances in biochemistry and the understanding of nucleic acids and protein synthesis. Bacteria were used as tools to understand genetics of higher organisms, why? Microbial Ecology, History of Microbial Ecology Sigler 9 Easy to grow Rapid growth Easy to manipulate Nucleic acid sequencing could help us understand how organisms are related = phylogeny… 1990s – present – Further advances in molecular biology, genetic fingerprinting and methodology that facilitates accurate and sensitive analysis of microbial communities. Microbial Ecology, History of Microbial Ecology Sigler 10