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Microbio 1-7
Microbiology in Agriculture Unimelb
| Question | Answer |
|---|---|
| General Role of Microorganisms | Important in nutrient cycling, digestion, plant health and food production Can cause disease, spoilage, or have beneficial effects |
| Types of Microorganisms | Metazoan Parasites, protists, algae, fungi, bacteria, viruses Eukaryotes and Prokaryotes |
| Metabolic Diversity | Microbes classified as photoautotrophs, chemoautotrophs, photoheterotrophs, chemoheterotrophs |
| Photoautotrophs | Solar energy source, CO2 carbon source |
| Chemoautotrophs | Chemical energy source, CO2 carbon source |
| Photoheterotrophs | Solar energy source, organic carbon source |
| Chemoheterotrophs | Chemical energy source, organic carbon source All pathogenic bacteria are chemoheterotrophs |
| Bacteria | Microscopic, single cellular, self-replicating organisms |
| Major Structures Present in Bacteria | Cell wall, endospores, capsules, flagella |
| Bacillus | Rod shaped bacteria |
| Coccus | Circular shaped bacteria |
| Species | Genetically and phenotypically similar group |
| Strain | Genetic variant within a species |
| Bacterial Nomenclature and Classification: Binomial System | Genus (capitalised) + species (lowercase), italicised in print |
| Microscopy and Staining | Purple gram stain = Gram positive Pink/red gram stain = Gram negative |
| Phylogenic Trees | Diagram that depicts the lines of evolutionary decent of different species, organisms, or genes from a common ancestor |
| Bacterial Genome Includes: | Chromosome, plasmids, transposons, phages |
| Binary Fission: Steps | 1. Cell replicates its DNA 2. The cytoplasmic membrane elongates, separating DNA molecules 3. Cross wall forms; membrane invaginates 4. Cross wall forms completely 5. Daughter cells |
| Types of Mutations | Lethal mutations Silent mutations Loss of function mutations Gain of function mutations |
| Silent Mutations | Do not result in a change of amino acid and have no effect on the phenotype of an organism |
| Loss of Function Mutations | Gene no longer encodes a functional protein |
| Gain of Function Mutations | The function of a gene is enhanced |
| Horizontal Gene Transfer | Non-genealogical transfer of genetic material from one organism to another |
| Horizontal Gene Transfer Includes: | Conjugation: Plasmid transfer between cells Transduction: Bacteriophage-mediated gene transfer Transformation: Uptake of free DNA by competent cells |
| Conjugation | Transfer between two cells involving direct contact. The donor bacterium transfers DNA to recipient by mating |
| Transduction | Transfer between two cells via a bacteriophage(virus) Donor DNA packaged into bacteriophage infects recipient bacterium |
| Transformation | Uptake of DNA from environment Recipient bacterium takes up extracellular donor DNA |
| Plasmids | Circular piece of extrachromosomal dsDNA Carry genes related to their replication and existence in a cell, but can carry other genes such as antibiotic resistance genes or virulence genes |
| Lytic Phages | Cause the host cell to burst (lyse) |
| Lysogenic Phages | Integrate into host chromosome and become prophages |
| Conjugative plasmids | -Virulence and drug-resistance plasmids are often conjugative plasmids - Conjugative plasmids encode genes required for conjugation |
| Truncated Plasmids | A plasmid DNA molecule that has had a portion of its sequence shortened or removed, resulting in a smaller size |
| Prokaryotic Gene Expression | -Transcription and translation occur almost simultaneously in the cytoplasm - When protein is no longer needed, transcription stops |
| Eukaryotic Gene Expression | - More complex due to intracellular organelles - Transcription occurs in the nucleus - Translation occurs in the cytoplasm outside of the nucleus |
| Why regulate gene expression? | -Bacteria exist in constantly changing environments - They need to quickly adapt to changing conditions |
| Constitutive Gene expression | -Constitutive genes are always expressed and are not regulated - Continually transcribed - 60-80% of genes are constitutive -Genes that are essential for the cell to function at all times |
| Regulating Gene Expression | -Regulated genes are only transcribed when needed - Bacteria have mechanisms for regulating catabolic and anabolic pathways |
| Catabolic | Breakdown complex molecules into simpler ones and release energy |
| Anabolic | Require energy to build complex molecules from simpler ones |
| Activators in Gene Expression | Increase transcription of a gene/operon |
| Repressors in Gene Expression | Turn off transcription of a gene/operon |
| Inducers in Gene Expression | Turn on transcription of a gene/operon |
| Prokaryotic Gene Expression is typically regulated by: | An operon, a collection of genes under a common control mechanism that are transcribed together to give a single mRNA |
| An operon typically includes: | Regulator Gene: encodes for a repressor protein Promoter: DNA sequence that binds RNA polymerase Operator: Where an active repressor binds Structural genes: encodes for enzymes and proteins |
| Repressor Operons | - Usually on - To turn them off, an active repressor protein binds to the operator and prevents RNA polymerase from transcribing the DNA |
| Catabolite Activator Protein (CAP) | -Transcriptional activator (increases transcription of a gene) |
| Lac Operon | Inducer - Ecoli uses lactose as an energy source when glucose concentrations are low - Lac operon encodes the genes needed to acquire and process lactose from the environment - It is turned on in the presence of lactose and absence of glucos |
| Inducible Operons | a gene regulation system in prokaryotes where expression is usually off but can be turned on by a specific molecule called an inducer. |
| Genealogical Inheritance | Vertical: mutations are passed from parent to daughter cells during binary fission |
| Steps for Virus infection and replication | 1. Attachment 2. Penetration 3. Uncoating 4. Transcription (early mRNA) 5.Translation (early protein) 6. Genome replication 7. Transcription (late mRNA) 8. Translation (late proteins) 9. Assembly 10. Release |
| DNA viruses replicate in: | The nucleus |
| RNA Virus Replication | Vary in replication based on strand polarity: +RNA can be directly translated -RNA requires transcription to +RNA before translation |
| Herpesviridae cause: | Latent infections (e.g. respiratory and neurological disease) |
| Parvoviridae are: | Stable in environment, cause systemic and enteric disease |
| Poxviridae are: | Transmitted via vectors or contact, cause skin lesions and high mortality in some species |
| Viral Infection Diagnosis | Embryonic egg inoculation, cell culture, PCR, point of care/stall-side/pen-side testing |
| Embryonic Egg Inoculation for diagnosis: | - Time consuming - Labour intensive - Technically difficult - Requires infectious virus |
| Cell Culture for diagnosis: | - Time consuming - Labour Intensive - Technically difficult - Infectious virus - Cytopathic effect |
| PCR for diagnosis: | -Rapid diagnosis - Specialised equipment - (may be) quantitative - Doesn't need infectious virus |
| Point of care/stall-side/pen-side testing for diagnosis: | - Rapid diagnosis - Specialised (cheap) equipment - (may be) quantitative - Doesn't need infectious virus - Trade off speed against sensitivity and specificity |
| Enteroviruses | Acquired by ingestion and replicate in gastrointestinal tract. |
| Respiratory viruses | Acquired by inhalation or by formatted and replicate primarily in respiratory tract |
| Arboviruses | Replicate in their haematophagus arthropod hosts and transmitted to vertebrate host by biting |
| Oncogenic Viruses | Acquired by close contact, injection and other means. Target specific tissues, become persistent and evoke host cellular transformation |
| Enveloped Viruses | -Must be in moist conditions - Spread in large droplets, secretions, transfusions, etc - Do not survive in adverse conditions (GIT) - Do not need lysis to spread within host - Antibody alone may not provide immunoprotection |
| Non-Enveloped viruses | - Can spread easily - Infective after drying - Survive adverse conditions (GIT) - Resistant to detergents - Antibody may provide immunoprotection |
| Herpesvirus | - Enveloped double stranded DNA viruses - Labile in environment - Easily inactivated by heat, detergents, pH, drying - Close or mucosal contact for transmission (droplet) - Lifelong latent infection |
| Bovine herpesvirus 1 | - Respiratory disease - Causes abortion |
| EHV- 1 | - Causes abortion - Neurodisease |
| Feline Herpesvirus | Respiratory disease |
| Gallid Herpesvirus 1 | Respiratory disease |
| Parapox Viruses: Off (scabby mouth) | Transmission: - Via direct or indirect contact - Infectious in scab for months Pathogenesis: - Epitheliotropic virus - Proliferative wart-like lesions |
| Myxomatosis | -Vector Transmission - Death often within 48 hours - 99% mortality rate for infected rabbits |
| Parvovirus Characteristics | - Small non-enveloped single stranded DNA virus - Replicate in nucleus - Require rapidly dividing cells - Very stable in environment - Very resistant |
| Feline Panleukopaenia | - Highly contagious, systemic and enteric disease - Bone marrow suppression, GIT signs, Cerebellar hypoplasia (foetus) |
| Canine Parvovirus 2 | - Highly contagious - Enteric disease - Haemmorhagic gastroenteritis Myocarditis (rare) |
| Porcine Parvovirus | Reproductive Disease |
Created by:
sakelleher29
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