Bacteria Outline Bacteria – Oldest, structurally simplest, most abundant forms of life – Only organism with prokaryotic cellular organization – The only members of the kingdom Monera (4800 different kinds) – Characteristics change depending on growth conditions – Maintenance of life depends on them – play vital role of productivity and as decomposers – Capable of fixing atmospheric N for use by other organisms – Used in production and fermentation of various food and as antibiotics and is being tested for insect control – Prokaryotes vs. Eukaryotes – Multi-cellularity – All bacteria fundamentally single celled – Sometimes cells adhere within a matrix to form filaments – Activities of bacterial colonies less integrated and coordinated than in multicellular eukaryotes Eukaryotes Bacteria Cell Size 10x size of bacteria 1 micrometer (m) diameter Chromosomes Membrane bound nucleus w/ chromosomes w/ nucleic acid & proteins No nucleus/chromosomes w/ DNA DNA contained in cytoplasm Cell Division and Genetic Remcombination Mitosis involving microtubules Sexual reproduction – meiosis/syngamy Binary fusion Lack of sexual reproduction – no equal participation Internal Compartementalization Respirational enzymes packed into mitochondria Corresponding enzymes bound to cell membranes Cytoplasm – no internal compartments/organelles (except ribosomes) No cytoskeleton Flagella Complex 9+2 structure of microtubules (whip-like motion) Simple w/ a single fiber protein flagellin Spins like a propellar Autotrophic Diversity Enzymes for photosyn. Packed in membrane-bound organelles (plastids) Only 1 type of photo. – release of O2 Enzymes bound to cell membrane Several patterns of aerobic/anaerobic photo. w/ formation of S, O, sulfate Chemosynthesis – process where certain bacteria obtain energy from oxidation of inorganic compounds and obtain C from CO2 – Bacterial Structure – Lypopolysaccharide – polysaccharide chain with lipids attached – Molecules of it deposited over layer of gram positive – forming outer membrane – Makes gram negative bacteria resistant to many antibiotics to which gram positive bacteria are susceptible – Capsule – gelatinous layer surrounding cell – Bacilli – straight, rod-shaped bacteria – Cocci – spherical bacteria – Spirilla – spirally coiled bacteria – Spores – single-celled bodies that grow into new bacterial individuals – Some bacteria change into stalked structures, grow long, branched filaments or form erect structures that release spores – Bacterial cells have simple structures – 2 kinds of cell walls – gram negative/positive – Cytoplasm of a bacterium contain no internal compartments/organelles & is bound by a membrane encased w/i a cell wall composed of 1/more polysaccharides – Pili – other kinds of hairlike outgrowths that occur on some bacteria cells – shorter than flagella – Help bacterial cells to attach to appropriate substrates – Endoscopes – resistant to environmental stress; may germinate & form new bacterial individuals after decades/centuries – Bacterial Variation – 2 processes lend variability to bacterial reproduction – Mutation – Because of the short generation time of bacteria whose populations often double in a few min., mutation plays important role in generating genetic diversity – Genetic Recombination – Transfer of genes from one cell to another as portions of viruses, plasmids, other DNA fragments *Intestinal bacterium: typhoid, dysentry, other diseases – Bacterial Ecology and Metabolic Diversity – Bacteria most abundant organisms in most environments – Obligate anaerobes – organisms cannot grow in presence of O2 – Facultative anaerobes – organisms that function as anaerobes/aerobes – Aerobes – organisms that require O2 – Autotrophic bacteria – Heterotrophs – get energy from organic material formed by other organisms (most bacteria) – Autotrophs – obtain energy from nonorganic sources – Photosynthetic bacteria – contain chlorophyll but not held in plastids *Cyanobacteria, green/purple sulfur bacteria, purple nonsulfur bacteria – Different colors caused by photosynthetic pigments – Chemoautotrophic bacteria – derive energy from the oxidation of inorganic molecules (N, S, Fe compounds, gaseous H) – Heterotrophic bacteria – Saprobes – bacteria that obtain nourishment form dead organic material – Autotrophic bacteria, capable of making their own food, obtain energy from light or the oxidation of inorganic molecules – Heterotrophic bacteria obtain energy from breaking down organic compounds made by other organisms – By-products of bacterial metabolism – Antibiotics – valuable – Botulism – food poisoning – Salmonella – gastrointestinal disease – N-fixing bacteria – N fixation – carried out by nodule-forming bacteria – Bacteria releases fixed N (when they break down proteins) – N cycle carried out exclusively by bacteria – Bacteria as plant pathogens – Most plant diseases caused by bacteria – Most bacteria that cause plant diseases are from a group of rod-shaped bacteria called pseudomonads * Citrus canker (Florida) – destroy citrus seedlings – Bacteria as human pathogens – Cholera, leprosy, tetanus, bacterial pneumonia, whooping cough, diptheria – Many diseases dispersed in food/water – Legionnairess Disease – Severe pneumonia – fatal in 15-20% of victims if untreated – Caused by legionella – small, flagellated, rod-shaped, gram/-, bacteria w/ pointed ends – Common in water – Attacks monocytes (type of white blood cell) – Destroyed with erythromycin treatment – Sexually Transmitted Diseases – Gonorrhea, syphilis – controlled w/ antibiotics (syphilis – penicillin) – Infections caused by Chlamydia trachomatis (bacteria) – Painful symptoms – causes sterility – Controlled w/ antibiotic tetracycline – Causes arthritis in young people – Dental Caries (decay) – Causes cavities in dental plaque (film on teeth) – Plaque consists of bacteria cells surrounded by polysaccharide matrix – Caused by diets high in sugar – Prevented w/ antibiotics – Bacterial Diversity – Archaebacteria – distinctive membranes, unusual cell walls, unique metabolic cofactors – Eubacteria – kingdom Archaebacteria belongs in – Methanogenic – prominent Archaebacteria – Produce methane from CO2 & H to obtain energy – Source of marsh gas – Reduce S to form hydrogen sulfide – Archaebacteria ancient group of prokaryotes that are different from eubacteria – seem to be direct ancestors of eukaryotes – Omnibacteria – rigid, rod-shaped, heterotrophic, gram/+ – Vibrios – comma-shaped that have single terminal flagellum – Obligate parasites – organisms that can live only as parasites – Rickettsias – bacteria causing Rocky Mountain spotted fever – Cyanobacteria – photosynthetic bacteria – bring about increase of free O2 in the atmosphere (crucial for eukaryotic evolution) – Produce accumulation of limestone deposits (stromatolites) – Phycobilins – accessory pigments that are blue & red & water soluble – Only in cyanobacteria, red algae, & cryptomonads – Mucilaginous sheath that can be different colors (blooms in H2O) – Fix atmospheric N in cells called heterocysts (especially important in rice fields) – Chloroxybacteria – photosynthetic bacteria – Fixes N – Biochemical characteristics give rise to chloroplasts of green algae – Mycoplasmas – Aphragmabacteria (phylum name) – Cause diseases in mammals & birds *Premature labor in women *Pneumonia – Treated with antibiotics – Spiroplasmas – cause plant diseases *Aster yellow – Both (spiro-/myco- plasmas) lack cell walls & cells bounded by 3-layered lipid membrane – Resistant to antibiotics & penicillin working to inhibit cell growth – Spirochaetes – long spirilla where flagella are inserted beneath outer lipoprotein membrane of gram/- outer cell wall – Agents of syphilis & yaws (disfiguring eye disease) *Lyme disease (inflammatory ailment)- treated w/ penicillin/tetracycline -Pseudomonads – straight/curved gram/- rods w/ 1/more flagella at one ent – Soil/water – break down organic compounds (autotrophic) – Plant pathogens – infections to people who eat the plants -Actinomycetes – produce spores by division of terminal, erect branches into chains of small segments – N fixing molecules formed at roots of flowering plants – Dental plaque, leprosy, tuberculosis – Ivermectin – antiparasitic agent, tetracycline, etc.
made from actinomycetes -Myxobacteria – gliding bacteria – unicellular rods – Cells embedded in slimy polysaccharides they excrete – Occur in soils – aerobes – N Fixing Aerobic Bacteria – gram/- and flagellated – Soil/water – converts N to a form which can be used by other organisms and itself – Fermenting bacteria – obligate anaerobe – N fixing -Chemoautotrophic bacteria – Chemoautotrophy – metabolism that depends on chemical sources of energy like methane, ammonia, hydrogen sulfide – Do not require sunlight – Use N compounds to gain energy (Nitrosomonas) – Oxidize inorganic S or Fe compounds to gain energy – Use methane/methanol.