Lecture 4: Types of Microorganisms PDF

LECTURE 4 Types of Microorganisms Ms. Peters  Types of Microbes Microorganisms are divided into several types: bacteria, archaea, protozoa, algae, fungi, viruses, and multicellular animal parasites (helminths). Each is characterized based on: – cellular composition – m...

LECTURE 4 Types of Microorganisms Ms. Peters  Types of Microbes Microorganisms are divided into several types: bacteria, archaea, protozoa, algae, fungi, viruses, and multicellular animal parasites (helminths). Each is characterized based on: – cellular composition – morphology – locomotion – reproduction Microbial Tree of Life Bacteria Bacteria are unicellular organisms Described as prokaryotic – (lack a nucleus) Reproduce by binary fission Can be classified based on: – Staining of the cell wall stain – Response to oxygen (aerobic, anaerobic, facultative anaerobes, microaerobes, capnophilic) – Energy Source (autotrophs, heterotrophs) Bacteria Cont. Exist in four major shapes: Bacillus Coccus (Escherichia coli) (Staphylococcus aureus) Spirilla Curved (treponema pallidum) (Vibrio cholerae) Archaea( Archaebacteria) Differ from ‘true’ bacteria in their cell wall structure and lack peptidoglycans. Prokaryotic cells with avidity to extreme environmental conditions Classified based on: – Habitat – Energy sources; bacteriorhodopsin. Archaea( Archaebacteria) Cont. Based on habitat Methanogens -thrive in methane rich environments Halophiles - live in salty environments Thermophiles - live at extremely hot temperatures Psychrophiles – Live at extremely cold temperatures Archaea( Archaebacteria) Cont. Based on energy source Phototrophic – utilizes unlight for energy production Chemical energy - utilize inorganic compounds like metal ions, hydrogen, ammonia E.g.: Pyrolobus Organotrophic Archaea - utilize organic compounds such as pyruvate, starch, maltose, e.g.: Pyrococcus Archaea( Archaebacteria) Cont Lonar Lake India that recently turned red due to the presence of salt-tolerant Haloarchaea populations in the lake. The photo pigment (for phototropism) of these archaea organisms is called ‘bacteriorhodopsin’ which is opaque to long wavelengths (red) and imparts this color to the lake. Image Credit: Mohammad Iqbal. Algae (cyanobacteria) Unicellular or multicellular eukaryotes Lives in water, damp soil, and rocks Reproduce asexually via binary fission, budding, or fragmentation. Produce oxygen and carbohydrates used by other organisms. (produce majority of the atmospheric oxygen!) Algae (cyanobacteria) Cont. https://www.researchgate.net/figure/Circular-economy-in-a-wastewater-treatment-system- with-microalgae-This-figure-was-made_fig3_356806768 Protozoa Unicellular eukaryotes- have a nucleus Possess complex organelles Obtain nourishment by absorption or ingestion through specialized structures. Protozoa have been classified based: mode of locomotion: Protozoa Cont. Mode of locomotion: – Flagellates use their whip-like structure to propel forward e.g. Giardia Lamblia – Ciliates have tiny hair that moves back and forth to produce movement e.g. Balantidium coli – Amoeboid move by pseudopodia or ‘false feet’ e.g. Entamoeba histolytica – Sporozoans –Nonmotile e.g., Plasmodium falciparum Protozoa Cont.. Fungi Classification of Fungi  Fungi Cont. Eukaryotic cells - have a true nucleus and do not photosynthesize Are either microscopic (moulds & yeast) or macroscopic (mushrooms) A few fungi are dimorphic- existing as yeast or mould depending on temperature The moulds are multicellular and consist of threadlike tubular structures called hyphae – Hyphae grow by tip extension – May be coenocytic or septate – Intertwine to form clumps of mycelia – Aerial hyphae and vegetative hyphae seen on agar  Fungi Cont. Types of hyphae Mycelium Vegetative and Aerial Hyphae Cell wall is composed of chitin Cell membrane contains ergosterol not cholesterol  Fungi Cont. All fungi are heterotrophic- acquire nutrients from organic materials Done through: – Decomposition – Symbiotic relationships with plants (symbionts) – Harmful relationships with a host (parasites). Spores are the reproducing bodies of moulds both sexually and asexually Yeast are unicellular and reproduce by budding –daughter cells may elongate to form sausage like pseudohyphae Fungi are classified based on colonial structure and method of reproduction Fungi Cont. Zygomycetes (Conjugation fungi) – Reproduce sexually producing zygospores and asexually producing sporangiospores (most common) – Most species are free living saprobes – Persistent contaminants in labs and food – E.g., Rhizopus spp. (Black bread mould) Fungi Cont. Ascomycetes (Sac fungi) – Reproduce sexually producing ascospores in asci and asexually producing conidiophores – Includes many important species Microsporum spp. causative agent of ringworm, Penicillium spp. source of antibiotics  Fungi Cont. Basidiomycetes (Club fungi) – Reproduce sexually producing basidiospores and asexually producing conidia – Septate hyphae – Fleshy fruit bodies are common – e.g., includes Mushrooms and Cryptococcus neoformans  Fungi Cont. Deuteromycetes (Fungi Imperfecti) – Reproduce asexually. The sexual reproductive stage is unknown – e.g., Candida spp. and Coccidiodes immitis Coccidiodes immitis Candida albicans Oral Thrush Fungi Cont. Fungal Mycoses (Diseases) Systemic: – Acquired primarily by inhalation – Is caused by dimorphic fungi – Usually confined to a specific geographical regions e.g., Histoplasma spp, Blastomyces spp, Cryptococcus spp, Coccidiodes spp Fungi Cont. Fungal Mycoses (Diseases) Subcutaneous: – Occurs mostly by wound puncture – It remains localized – E.g., Sporotrichosis (“rose gardener’s disease”) Caused by Sporothrix schenii Causes localized lesions Is endemic in South America Fungi Cont. Fungal Mycoses (Diseases) Cutaneous: – They invade keratinized and cutaneous tissue – i.e., skin, hair and nails – Dermatophytes may be responsible – e.g., Trichophyton spp., Epeidermophyton spp, Microsporum spp. – Can also be caused by Candida spp. , Aspergillus spp. Fungi Cont. Fungal Mycoses (Diseases) Superficial: – Affects superficial surfaces of the skin and hair – Is of cosmetic importance only – Tend to reappear – E.g. tinea versicolor (‘lotta’) which is caused by Malassezia furfur Fungi Cont. Fungal Mycoses (Diseases) Opportunistic: – Only affects immunosuppressed patients – Most are commensals – Has a very low virulence except for C. neoformans – Found in bird droppings; particularly pigeons C. neoformans Fungi Cont. Fungal Mycoses (Diseases) Mycotoxins: – Amanita mushroom causes mycetimus – Severe cramping – Afloatoxin released by Aspergillus flavus Viruses Viruses are noncellular entities Viral genome consists of a nucleic acid core of either DNA or RNA surrounded by a capsid (protein coat) A nucleocapsid refers to both the capsid and the nucleic acid. Although viruses are classified as microorganisms, they are not considered living organisms. Viruses often infest prokaryotic and eukaryotic cells causing diseases. Viruses Classified according to nucleic acid: DNA or RNA Double stranded or single stranded Linear or circular Positive or negative sense RNA According to capsid Icosahedral Helical Presence or absence of an envelope Viruses Baltimore classification – a classification system that places viruses into one of seven groups depending on a combination of: nucleic acid (DNA or RNA), strandedness (single-stranded or double-stranded) sense method of replication.  Viruses Baltimore classification – I: dsDNA viruses e.g., Adenoviruses, – II: ssDNA viruses (+ strand or "sense") e.g., Parvoviruses – III: dsRNA viruses e.g., Reoviruses – IV:(+)ssRNA viruses (+ strand or sense) e.g., Coronaviruses – V: (−)sssRNA viruses (− strand or antisense) RNA e.g., Orthomyxoviruses – VI: ssRNA-RT viruses (+ strand or sense) RNA with DNA intermediate in life-cycle (e.g., Retroviruses) – VII: dsDNA-RT viruses DNA with RNA intermediate in life-cycle (e.g., Hepadnaviruses) Viruses Viruses DNA viruses HHAPPPy: – Herpes, Hepadna, Adeno, Papova, Parvo, Pox – Most are double stranded, Icosahedral and replicates in the nucleus – Except for Parvoviridae which is single stranded – Poxviridae has a complex nucleocapsid and replication occurs in the cytoplasm  Viruses Three of the DNA viruses have envelopes: Herpes, Hepadna and Pox Three are naked viruses Papova, Adeno and Parvo (PAP)  Viruses Most RNA viruses are single stranded (half are positive and half are negative, enveloped, helical symmetry, replicates in the cytoplasm Multicellular Eukaryotic Parasites Major groups of parasitic helminths include: - platyhelminths (flatworms) - cestodes (tapeworms) - trematodes (flukes) - nematodes (roundworms). Although they are not microorganisms by definition Live a part of their life cycle in microscopic form. Are of clinical importance Multicellular Eukaryotic Parasites Multicellular Eukaryotic Parasites Nematodes – Occur as parasites in animals and plants or as free-living forms in soil, fresh water, marine environments, – Bilaterally symmetrical, elongate, Tapered at both ends, non segmented, white worms with anterior mouth and posterior anus – Sexes are separate (not hermaphrodites)- females are larger – Cause of some of the most debilitating the disfiguring diseases in humans Multicellular Eukaryotic Parasites Nematodes E.g., Ascaris lumbricoides  Multicellular Eukaryotic Parasites Cestodes – Parasitic in all stages of life – Majority are long, segmented flattened dorsoventrally, creamy to white in color and tape-like hence the name tapeworms. Scolex (head) has suckers and sometimes hooks for attachment to organs – Size varies from a few mm to several meters. – Adults live attached to the mucosa of the small intestine of man and animals. – Larval stages are parasitic in the tissues or body cavities of vertebrate or invertebrate hosts.  Multicellular Eukaryotic Parasites The adult consist of: Scolex or head organ of attachment. Neck region of growth &proliferation. Proglottids or segments (immature, mature and gravid one which contain eggs). 4 cupped suckers symmetrically arranged, Sexes are not separate (hermaphrodites) Body cavity is absent. Multicellular Eukaryotic Parasites Trematodes: – Dorso-ventrally flattened and leaflike in shape, unsegmented, bodies covered with tegument and have two suckers: one oral and one ventral. Blind intestinal tracts, hermaphrodites except for Schistosoma spp.