ET-Ch10 - Classification of microorganisms(and everything...

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Unformatted text preview: Classification of microorganisms (and everything else for that matter) - TAXONOMY - the science of the classification of organisms - Purpose — to show e\.-'oluti011ary relationships between groups — to provide a means of identifying organisms Two methods of classification ' Most scientists favor a PHYLOGENETIC classification scheme; this reflects the actual ancestry (et.--'oluti~<.3~nar}r relationships) between different organisms ' Phenetics is an alternative method, in which classification of organisms is based solely on observable characteristics, and the goal is more practical - identification and common language. The Five-kingdom System Monera - unicellular prokaryotes (bacteria) (based upon cellular organization) Prctista - unicellular eukaryotes (protozoar algae) (based upon cellular organization) Fungi - multicellular heterotrophs with extenial digestion (yeastsflmoldsj mushrooms) (based upon nutritional pattern) Plantae - multicellular autotrophs (plants) (based upon nutritional patteni) Animalia - multicellular heterotrophs with intenial digestion (animals) (based upon nutritional pattem) KINGDOM MONERA /\ DOMAIN BACTERIA DOMAIN ARCHAEA " nts Fungi A“ I I'I'IHI 5 ~ ....'_ Fla \ DOMAIN EUKAR‘I’A x The three Domains A domain is considered to be a new level apart from Kingdom, based on the fact that cells are really of three fundamental types: Eukarya (eukaryotes) Bacteria (most bacteria) Archaea (archaebacteria) - no peptidoglycan in cell walls, extreme environments and strange biochemistry. Molecular studies of their DNA reveal they are not very related to eub acteria. KIHGDOM MOHERA DOMAIN BACTERIA DDMAIN ARCHAEA DOMAIN EU KARYA “I nts Fungi Anlmals h Fla .-" ..-" “- The Linnaean Taxonomic Hierarchy . Traditionally has 7 tiers (8 if you count the domains) - Domain, Kingdom, Phylum (Division), Class, Order, Family, Genus, Species . The tiers go from most inclusive to least, until you reach the species or specific name, usually denoted as genus and species. This is called a binomial designation, and lVIUST BE underlined or amazed. Also, the genus name must be capitalized. . Examples - Escherichia colt, Home sapfens Examples: Classify this! Human being Domain - Euliarya Kingdom - Animalia Phylum - Chordata Class - Mammalia Order - Primates Family - Hominidae Genus - Home species - sopr'ens Dog Domain - Eul<zarya Kingdom - Animalia Phylum - Chordata Class - Mammalia Order - Camivora Family - Canidae Genus - Cam's species -famrlrarrs Examples: Classify this! Hum an being Dcmain - Eukarya Kingdcm - Animalia Phylum - Chcrdata Class - Mammalia Order - Primates Family - Heminidae Genus - Home species - sapieas A bacterium like E. can? Dcmain - Bacteria Kingdcm - Mcnera Phylum - Gracilicutes Class - Scctcbacteria Order - Entercb acteriales Family - Entercbacteriacieae Genus - Escherichia Species - 0031' E. 1ire-::he-Lee - - F ween 5Lil’rur .- .. . . - baLieria LII l'_—'|:'_‘r'| I'l|'_.'-I"|=-.|.,]”|.,” iJgi.:_I.-:_‘ri.-_J_- Chlamydies Pmteuiziacteria Simplified pihylizngern:F of selected groups {kingdemsi of the Domain Bane ria. THEE 0F BACTERIAL PHYLOGENY Bacteria are classified according to... Bergeyis Manual of Bacteriology In 1923. the first edition of the Manual was published under the auspices of the organization that is today the American Society for Microbiology (Dr. David H. Bergey was the Chairman). The official title of this publication is “Bergeyis Manual of DETERMINATIVE Bacteriology.“ The latest edition was published in 1994. It should be clear that through much of its history. the classification was performed based on “observable characteristics”. or phenetics. although eare was taken to try to reflect phylogeny as mueh as was possible. Characteristics used to classify bacteria - Morphological characteristics (shape, etc.) - Differential Staining (Gram stain) - Nutritional Pattern - Relationship with oxygen - Biochemical characteristics (eg, catalase +I'-) - Serological analysis - ability of specific antibodies to react with specific microbe - Phage typing - can bacteria be infected by the same phage - Protein and DNA sequencing are becoming more popular - powerful! (These are not considered “observable characteristics”: and are the basis for more modem classification schemes.) Bacterial classification is changing! * Since the advent of sophisticated DNA, RNA and protein analysis techniques, more data on phylogeny has emerged, and is continually emerging. ' Therefore, the first edition of “Bergey”s Manual of SYSTEMATIC Bacteriology” was published during the 1980s to reflect phylogeny - the categories in this book are quite different, and it is clear that the DETERMlNATIVE Manual has limitations. It is also useful, however, if your goal is identification, and as the transition to a fully phylogenetic classification is realized. The second edition of the SYSTEMATIC Manual was finished in 2003. . Another philosophical problem - what is a species anyway? - A species is usually defined as a group of potentiallyr interbreeding organisms that can produce viable offspring. - Does this work for bacteria? ' No. - Why? - Sex again! I I think you have gathered Bacteria do not have sex! ! ! I! So, a bacterial species is usually defined as a population of cells with similar characteristics. How similar? It's sort of subjective!!! The current convention is that more than 3% difference in overall genome sequence reflects membership in a different species. But, remember - both the sexual and non-sexual definitions are just ways of getting at similarity Viral classification - Traditionally, as we know, viruses are not considered alive and thus are not classified in any of the preceding groups. - However, we still need to identify types of viruses for clinical and evolutionary reasons (e.g. HIvI) - So, a viral species is defined as a population of viruses that have similar characteristics. - Some scientists have proposed that viruses get classified according to whom they can infect - makes sense evolutionarily, but not in common usage. ...
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