ECOL 182R 1st Edition Lecture 6 Outline of Last Lecture I Early views of evolution II What is evolution III Science Religion a Scientific facts vs theories IV What is evidence for evolution Outline of Current Lecture I Major divisions of life Prokaryotes vs eukaryotes five kingdoms 3 domains II Ecological roles of bacteria III Metabolic not morphological diversity IV Bacteria V Archaea Current Lecture Dividing up life into major groups VI Historically life was divided into bacteria and everything else Formally expressed as prokaryotes and eukaryotes VII The differences is the presence eukaryotes or absence prokaryotes of a nuclear membrane VIII When a nuclear membrane is present mRNA must leave nucleus in order to be translated into proteins In prokaryotes we have coupled transcription translation IX So bacteria and eukaryotes formed the two major branches of life Starting in mid 1970s Carl Woese challenged this view of a single group of bacteria Bacteria had historically been characterized by rough morphological features and a series of standard metabolic tests profiles Woese s early rRNA sequencing small fragments less than 20 base pairs long suggested two major groups in bacteria He initially proposed the term Archaebacteria shortened to Archaea today for a group of prokaryotes living in very strange environments with very distinct rRNAs Three Domains of Life Controversial at first but then most believed Woese was correct Thus there are 3 not two fundamental life forms Bacteria Archaea and eukaryotes Which means is that an Archaea and a bacteria are as distant evolutionary from each other as humans are from a bacteria Bacteria vs Archaea Archaea metabolism like bacteria Archaea information processing transcription and translation DNA packaging like eukaryotes Thus Archaea share fundamental features of each Bacterial Diversity About 10 13 cells make up your body but living on it are about 10 12 bacterial cells on your skin and about 10 14 bacterial and archaeal cells in your digestive tract Bacteria and archaea live almost everywhere Only 5000 species have been named but biologists are certain millions exist Microbiology is the study of microbes microscopic organisms Bacteria Disease No archaea are known to cause disease in humans Bacteria that because disease are called pathogenic Bacterial induced diseases plau major ecological roles Experiments of Robert Koch became the basis for the Germ Theory of Disease which says infectious diseases are caused by bacteria viruses acellular particles that parasitize cells Koch s Postulates used to confirm a causative link between a specific infectious disease and a specific microbe 1 The microbe must be present in a person who has the disease absent from healthy people 2 The organism must be isolated grown in a pure culture away from the host organism 3 If organisms from the pure culture are injected into a healthy animal the disease symptoms should appear 4 The organism should be isolated from the diseased animal again grown in pure culture and demonstrated to be the same as the original organism Bacteria Disease continuted In industrialized countries between sanitation nutrition have definitely reduced mortality rates due to infectious disease around 1900s In addition the discovery of antibiotics molecules that kill bacteria their widespread use allowed physicians to combat most bacterial infections However overuse of antibiotics leads to antibiotic resistant strains of bacteria Bacteria can clean up pollution Toxic pollutants are toxic don t dissolve in water and accumulate in sediments Bioremediation is using bacteria archaea to degrade pollutants Uses 2 strategies 1 Fertilizing contaminated sites to encourage the growth of existing bacteria and archaea that degrade toxic compounds 2 Adding specific species of bacteria and archaea to contaminated sites Ecological diversity of Bacteria They re found everywhere Bacteria or archaea that live in high salt high temp low temp or high pressure habitats are called extremophiles Understanding extremophiles could help explain how life on Earth began Bacteria and archaea can live in extreme environments and use toxic compounds as food because they produce extremely sophisticated enzymes Their complex chemistry and abundance make bacteria and archaea potent forces for global change Working with bacteria Historically bacteria had to be cultures to be characterized Most are hard to culture so they were overlooked Even if easily cultured bias towards certain culture conditions Ex Human bacteria better known than deep sea bacteria DNA Genomics revolutions Universal primers are allowed rRNA sequences to be obtained without having to culture an organism Most molecular phylogeny of bacteria was based on ribosomal RNA sequences but later supplemented by additional genomic info Now we can sequence a whole bacterial genome in just hours or days without having to culture an organism Although tiny microbes heavily impact the biosphere The Oxygen Revolution No free molecular oxygen for first 2 3 billion years of Earth Cyanobacteria a lineage of photosynthetic bacteria were the 1st organisms to perform oxygenic photosynthesis Cyanobacteria were responsible for changing the Earth s atmosphere to one with a high concentration of oxygen All because this organism polluted the planet The Nitrogen Cycle All organisms need nitrogen to synthesize proteins nucleic acids Although it s abundant most organisms can t use it directly All eukaryotes must obtain it as ammonia or nitrate The only organisms capable of converting molecular nitrogen to ammonia nitrogen fixation are specific bacteria Certain aquatic cyanobacteria can fix nitrogen On land nitrogen fixing bacteria live in close association with plants often taking up residence in root structures called nodules Metabolism Organisms need energy and carbon to grow Must somehow acquire energy to make ATP Turn ADP to ATP Photosynthesis Eat something organic They must somehow get make molecules with carbon carbon bonds Autotrophs make their own carbon containing compounds turn CO2 into C C bonds Heterotrophs live by consuming them humans Metabolic Diversity All organisms must get chemical energy in form of ATP and get carbon compounds that can serve as building blocks for synthesis of cellular components Bacteria archaea have 3 sources for ATP production light organism molecules eat something or inorganic molecules eat also Phototrophs use light energy ATP produces by