Microbial Classification, Part II PDF

Microbial Classification, Part II Dr. Moroianu Diversity in eukaryotes 2 Classification of Eukaryotes Protista: a catchall kingdom for a variety of organisms; autotrophic and heterotrophic Grouped into clades based on rRNA Fungi: chemoheterotrophic; un...

Microbial Classification, Part II Dr. Moroianu Diversity in eukaryotes 2 Classification of Eukaryotes Protista: a catchall kingdom for a variety of organisms; autotrophic and heterotrophic Grouped into clades based on rRNA Fungi: chemoheterotrophic; unicellular or multicellular; cell walls of chitin; develop from spores or hyphal fragments Plantae: multicellular; cellulose cell walls; undergo photosynthesis Animalia: multicellular; no cell walls; chemoheterotrophic 3 Protists clarification Groups of protists do not share a common ancestor with each other that is not also shared with plants, fungi, and animals Protists are a group of all the eukaryotes that are not fungi, animals, or plants 4 Visualization of phylogenetic tree 5 Algae- photosynthesizing protists Not a taxonomic group (mixed among other groups) Unicellular or filamentous photoautotrophs Lack roots, stems, and leaves Mostly aquatic Water is necessary for growth and reproduction All reproduce asexually Multicellular algae can fragment or reproduce sexually via alternation of generations 6 Selected phyla of algae Brown algae (kelp) Cellulose and alginic acid cell walls Multicellular and macroscopic Produce algin-thickener used in foods 7 Selected phyla of algae Red algae Have branched thalli Most are multicellular Harvested for agar and carrageenan Some produce a lethal toxin 8 Selected phyla of algae Green algae Cellulose cell walls Unicellular or multicellular Chlorophyll a and b Store starch Gave rise to terrestrial plants 9  Selected phyla of algae Diatoms Pectin and silica cell walls Unicellular or filamentous Store oil Produce domoic acid-cause neurological disease Contracted by swimming in water affected by algal blooms Symptoms include: gastrointestinal cramping, nausea and vomiting, seizures, death, disorientation and memory loss 10 Selected phyla of algae Dinoflagellates Cellulose in plasma membrane Unicellular Neurotoxins (saxitoxins) cause paralytic shellfish poisoning § Fish contamination and death § Tingling of lip and tongue Dinoflagellates are the most common cause of algal blooms in salt water Cause red tide 11  Selected phyla of algae Oomycota (water molds) “Pseudo-fungi” are more closely related to brown algae and diatoms than to the true fungi Chemoheterotrophic Produce zoospores Use flagella for movement Decomposers and plant parasites Phytophthora infestans was responsible for Irish potato blight P. cinnamoni infects Eucalyptus P. ramorum causes “sudden oak death” 12 Protozoa – nonphotosynthesizing protists Unicellular eukaryotes Inhabit water and soil Feeding and growing form is a trophozoite Asexual reproduction is by fission, budding, or schizogony (multiple fission) Sexual reproduction is by conjugation Some produce a cyst to survive adverse conditions 13  Categorizing protozoa Require a large supply of water Many have an outer protective pellicle, requiring specialized structures to take in food Ciliates wave cilia toward mouthlike cytosome Amebae phagocytize food Food is digested in vacuoles and wastes eliminated through an anal pore 14 Key groups in protozoa Feeding grooves (Excavata) Parabasalids Diplomonads Undulating membrane; no cyst Parabasalids stage Euglenozoa Euglenozoa Amebae Photoautotrophs or facultative chemotrophs Apicomplexa Hemoflagellates-transmitted by Ciliates bites of blood-feeding insects Diplomonads Slime molds No mitochondria; multiple flagella 15 Super kingdom Excavata 16 Amebae Move by extending pseudopods Entamoeba histolytica-causes amebic dysentery (infectious diarrhea) Acanthamoeba-infects corneas and causes blindness Balamuthia-deadly neurological disease 17  Apicomplexa Obligate intracellular parasites Toxoplasma gondii-transmitted by cat feces; causes fetal infections Contracted by touching cat feces and touching your mouth, NOT by petting, holding, or even being licked by a cat Can also be transmitted through eating raw meat or unwashed fruit/vegetables Cryptosporidium-transmitted via feces; causes waterborne illness 18 Apicomplexa - Malaria Plasmodium-causes malaria Sexually reproduces in the Anopheles mosquito A mosquito injects a sporozoite into its bite, and the sporozoite undergoes schizogony in the liver; merozoites are produced Merozoites infect red blood cells, forming a ring stage inside the cell Red blood cells rupture, and merozoites infect new red blood cells 19 Ciliates Move by cilia arranged in precise rows Balantidium coli is the only human parasite; causes dysentery Passed on if individual with dysentery uses bathroom, doesn’t wash hands, and touches food and other surfaces 20 Slime mold Cellular slime molds Resemble ameba Ingest fungi and bacteria by phagocytosis unicellular Plasmodial slime molds Mass of protoplasm with multiple nuclei; moves as a giant ameba Enclosed within single membrane without walls, forming one large cell “Super cell” with multiple nucelli 21 Slime molds in action 22  Helminths Helminths are parasitic worms Eukarya Kingdom Animalia Two phyla: Platyhelminthes (flatworms) Nematoda (roundworms) 23 Characteristics of Helminths Multicellular eukaryotic animals Specialized to live in hosts May lack digestive system Reduced nervous system Reduced or lacking locomotion Complex reproductive system Technically not microorganisms, however we study them in this field as they cause diseases and their eggs and larvae are microscopic 24 Platyhelminths (flatworms) Trematodes (flukes) Flat, leaf-shaped Ventral and oral sucker Absorb food through cuticle covering Cestodes (tapeworms) Scolex-head that has suckers for attachment Absorb food through cuticle Can be up to 12 feet long and live for years Primarily contracted after eating raw or undercooked meat and fish, also can be caused by poor hygiene 25 Cestoda-tapeworm 26 Nematoda (Roundworms) Roundworms Cylindrical; complete digestive system Free-living and parasitic Eggs infective for humans Ascaris lumbricoides-infects human intestines Heartworm, Dirofilaria immitis, transmitted via mosquitoes to primarily dogs May also be given to cats, ferrets, and some wild animals such as wolves, coyotes, and fox 27 Arthropods as Vectors Arthropods are animals with segmented bodies, hard external skeletons, and jointed legs Vectors are arthropods that carry pathogenic microorganisms Representative classes: Arachnida-eight legs Crustacea-four antennae Insecta-six legs 28  Arthropods as Vectors Mechanical transmission Arthropod carries pathogen to host without being infected themself Biological transmission Pathogen multiplies in the vector Definitive host Microbe’s sexual reproduction takes place in Temps above 50F start emerging Active once ground temp is 45F the vector At 80F full force Increased breeding and activity when temps 70-90 F 29 Viruses- General Characteristics Obligatory intracellular parasites Require living host cells to multiply Contain DNA or RNA Contain a protein coat No ribosomes No ATP-generating mechanism 30 Virus host range Virus host range- spectrum of host cells a virus can infect Most viruses infect only specific types of cells in one host Determined by specific host attachment sites and cellular factors Bacteriophages-viruses that infect bacteria 31 Viral structure Virion-complete, fully developed viral particle Nucleic acid-DNA or RNA can be single- or double-stranded; linear or circular Capsid-protein coat made of capsomeres (subunits) Envelope-lipid, protein, and carbohydrate coating on some viruses Spikes-projections from outer surface, assist with attachment 32 Virus taxonomy Genus names end in -virus Family names end in -viridae Order names end in -ales Viral species: a group of viruses sharing the same genetic information and ecological niche (host) Descriptive common names are used for species Subspecies are designated by a number 33  Studying viruses Viruses must be grown in living cells Bacteriophages are grown in bacteria Bacteriophages form plaques, which are clearings on a lawn of bacteria on the surface of agar Each plaque corresponds to a single virus; can be expressed as plaque-forming units (PFU) 34 Studying animal viruses In living animals In embryonated eggs Virus injected into the egg Viral growth is signaled by changes or death of the embryo In cell cultures Tissues are treated with enzymes to separate cells Virally infected cells are detected via their deterioration, known as the cytopathic effect (CPE) Continuous cell lines are used 35 Viral multiplication For a virus to multiply: It must invade a host cell It must take over the host’s metabolic machinery One-step growth curve 36 Multiplication of Bacteriophages Lytic cycle Phage causes lysis and death of the host cell Lysogenic cycle Phage DNA is incorporated in the host DNA Phage conversion Specialized transduction Some viruses reproduce using both methods, while others only use the lytic cycle 37 Bacteriophages: Lytic Cycle 1. Attachment: phage attaches by the tail fibers to the host cell 2. Penetration: phage lysozyme opens the cell wall; tail sheath contracts to force the tail core and DNA into the cell 3. Biosynthesis: production of phage DNA and proteins 4. Maturation: assembly of phage particles 5. Release: phage lysozyme breaks the cell wall 38 39 Bacteriophage: Lysogenic Cycle Lysogeny: phage remains latent Phage DNA incorporates into host cell DNA Inserted phage DNA is known as a prophage When the host cell replicates its chromosome, it also replicates prophage D NA Results in phage conversion-the host cell exhibits new properties Specialized transduction Specific bacterial genes transferred to another bacterium via a phage Changes genetic properties of the bacteria 40 41  Animal viruses 1. Attachment: viruses attach to the cell membrane 2. Entry by receptor-mediated endocytosis or fusion 3. Uncoating by viral or host enzymes 4. Biosynthesis: production of nucleic acid and proteins 5. Maturation: nucleic acid and capsid proteins assemble 6. Release by budding (enveloped viruses) or rupture 42 Biosynthesis of DNA viruses DNA viruses replicate their DNA in the nucleus of the host using viral enzymes Synthesize capsid in the cytoplasm using host cell enzymes 43 DNA Viruses Poxviridae Double-stranded DNA, enveloped Cause skin lesions Vaccinia and smallpox viruses (Orthopoxvirus) Contagious by household contact Eradicated due to successful vaccine 44  DNA viruses Herpesviridae Double-stranded DNA, enveloped HHV-1 and HHV-2-Simplexvirus; cause cold sores HHV-3-Varicellovirus; causes chickenpox HHV-4-Lymphocryptovirus; causes mononucleosis HHV-5-Cytomegalovirus HHV-6 and HHV-7-Roseolovirus HHV-8-Rhadinovirus; causes Kaposi’s sarcoma 45  DNA viruses Papovaviridae Double-stranded DNA, nonenveloped Papillomavirus Causes warts Can transform cells and cause cancer Human papillomavirus (HPV) Transmission is primarily through skin-to-skin or skin-to-mucosa contact 46 DNA viruses Hepadnaviridae Double-stranded DNA, enveloped Hepatitis B virus Liver infection Use reverse transcriptase to make DNA from RNA 47 RNA viruses DNA viruses are mostly double-stranded while RNA viruses are single- stranded RNA mutation rate is higher than the DNA mutation rate DNA replication takes place in the nucleus while RNA replication takes place in the cytoplasm DNA viruses are stable while RNA viruses are unstable 48 RNA viruses Enterovirus Poliovirus and coxsackievirus Rhinovirus Common cold Hepatitis A virus Rubivirus Rubella Lyssavirus Rabies 49 Viruses and cancer Several types of cancer are caused by viruses May develop long after a viral infection Cancers caused by viruses are not contagious Oncogenes transform normal cells into cancerous cells Oncogenic viruses become integrated into the host cell’s DNA and induce tumors Human tumor viruses account for an estimated 12% to 20% of cancers worldwide Epstein-Barr virus, human papilloma virus, hepatitis B virus, and human herpes virus-8 are the most common cancer causing viruses 50 Another infectious agent: Prions Prions- Proteinaceous infectious particles Induce abnormal folding of prion proteins that are found most abundantly in the brain Inherited and transmissible by ingestion, transplant, and surgical instruments Transmissible Spongiform encephalopathies (TSE, prion disease) Mad cows disease, Creutzfeldt-Jakob disease Spread through meat consumption and bone meal 51 Another infectious agent: Prions Symptoms include: confusion and dementia, followed by memory loss, hallucinations, personality changes, speech impairment, motor impairment, and seizures. Fatal within days to years Research now finding increasing evidence that prions may be the cause of neurodegenerative diseases (NDs), including Alzheimer's, Parkinson's and Lou Gehrig's diseases 52