Microbiology Dr Karen Sullivan Office Phone 578 7192 Office Address 516 Life Sciences Bldg Email ksulli2 lsu edu Chapter 1 The Microbial World Chapter Overview The microbes Microbial genetics Microbial metabolism and ecology Microbes and disease The microbes What is microbiology the study of organisms too small to been with the naked eye the study of microbes What are microbes forms of life too small to be seen with the naked eye bacteria fungi algae protists small pox digesting food The microbes The field of microbiology examines how microbes interact with humans Some are pathogenic cause disease Some are beneficial normal flora Interact with food Some destroy crops corn rust late blight Irish potato famine Some make foods beer bread cheese how they can be used BY humans make antibiotics vitamins insulin Etc The microbes If microbiology is the study of life what is the basis for life characteristics of life metabolism all chemical reactions occuring in cell or growth reproduction genetic variation evolution responses adaptation to the external environment homeostasis maintain internal state at an acceptable body level The microbes What macromolecules major units are needed for life The microbes Polypeptides proteins one of most important functions is as catalysts of chemical reactions Some are structural Example enzyme RNA polymerase produce RNA from DNA template in the process of transcription The microbes Polysaccharides polypeptides embedded in lipid bilayer forming a cell s cytoplasmic plasma membrane separates the external environment from the interior of the cell The microbes Nucleic acids DNA RNA storehouses of genetic information comparisons of DNA sequences are used to separate life forms into three large groups known as domains The microbes Up until the 1970s organisms were placed into one of two categories prokaryotes or eukaryotes depending whether or not they had membrane bound organelles mitochondria nucleus The microbes In the 1970s DNA sequencing was used to compare sequences of ribosomal RNA genes in different organisms This led to a new scheme of organizing life into three domains Bacteria Archaea and Eukarya The microbes Each of the thee domains has some similarities and some differences to the others The microbes What about viruses Technically viruses aren t considered to be alive They don t replicate outside of a host cell They have little to no biochemical activity outside of a host cell They are inert and nonreactive outside of a host cell Microbiology still studies viruses since they are too small to be seen with the naked eye The microbes Why study microbes fast cheap and easy to grow Can produce enzymes and molecules for industrial medical uses ex insulin Have small numbers of genes simpler to study Bacteria generally only have one single chromosome Genetic manipulation of single celled bacteria is easier than with multicellular eukarya Microbial genetics What can studying the genetics of microbes teach us about the evolution of life on Earth early environment on Earth was drastically different than today Very little oxygen in the atmosphere surface of planet was a soup of chemicals This environment led to initial synthesis of first forms of macromolecules and their use in primitive single celled life Microbial genetics Multicellular fossils dating to about 0 5 billion ybp years before present have been found meaning microbes dominated the planet for approximately 3 5 billion years Some microbial fossil records do exist largely in fossilized mats stromatolites discovered in Australia Microbial genetics So how did the first microbial life arise 1950s a grad student named Stanley Miller worked with his mentor Harold Urey to simulate the spark that might have started forming organic molecules from the primordial soup Microbial genetics molecules alone aren t life so how did early organic molecules change into the four macromolecules of cells today Iron containing surfaces may have helped provide the right environments by sticking the molecules to their surfaces early life would need to have genetic information ability to catalyze biochemical reactions and way of separating the cell interior from the external environment Are there molecules or structures that might satisfy those requirements Yes Microbial genetics Yes Some RNA molecules have the ability to catalyze reactions ribozymes combination of ribonucleic acid enzymes RNA could serve dual purpose of genetic information storage AND catalyzing reactions Microbial genetics what about separating interior from exterior of cell Lipid layer know as a micelle may have been early form of plasma membrane could have formed a crude way of separating interior contents from the external environment Microbial genetics basic idea of how microbial life arose on Earth Early conditions formed RNA and micelles These came together into a primitive cell using RNA for storing genetic info and coding Primitive cells eventually changed from using RNA to DNA for storing genetic information Microbial genetics So then when how did eukaryotes appear Endosymbiotic theory Primitive prokaryotic microbes ingested other microbes starting a symbiotic relationship forming the first basic eukaryotes microbes that could use oxygen for a respiratory process similar to E coli to produce chemical energy became mitochondria microbes that could fix carbon dioxide into organic molecules using light energy similar to cyanobacteria became chloroplasts Microbial genetics Evidence supporting endosymbiotic theory Mitochondria and chloroplasts have 2 membranes Same as some prokaryotes possess their own DNA ribosomes are about the size of a prokaryotic cell E coli and cyanobacteria divide by a process similar to bacteria Replicate on their own Microbial genetics Bacteria and humans today use double stranded DNA not single stranded RNA for storage of genetic information Why the change dsDNA provides a backup copy of the genetic information in case of a problem DNA is more stable than RNA Less likely to be degraded by enzymes that degrade single strands Microbial genetics importance of RNA in basic information flow of modern cells highlights its prehistoric importance DNA is transcribed into a working copy in the form of messenger m RNA mRNA is translated into the proteins Other forms of RNA tRNA rRNA are also important showing the versatility of RNA molecules for life processes Microbial genetics how do we use this information to study the genetics