Week 3, Viruses, classification, and ID

Names consist of two parts: the genus, which can be shortened to the first letter of the genus, followed by the species; e.g. Bacillus subtilis = B. subtilis

Infectious misfolded proteins devoid of nucleic acids that cause disease in vertebrates and fungi.

→ Shape of virion (round, rod, etc) → Host → Genome properties (DNA/RNA, sense, etc)

→ Pin moulds common in soil and decaying organic matter → Form mould on bread and soft rot in fruit and veg → Large, dark-coloured sporangia visible to the naked eye → Non-motile spores → Root-like rhizoids are present at the base of the hypha that bears a sporangium (this features helps distinguish it from Mucor species) → The sporangium has a distinctive cullumella (swollen septum at the apex of the hypha that bears the sporangium)

→ Size → Hyphae (septate/aseptate) → Spores → Spore-bearing structures

→ Morphology → Other growth-dependent methods (physiology, metabolic tests, chemical composition, etc) → Molecular biology

→ Cause grey mould of fruits, vegetables, and ornamentals; and bunch rot or noble rot in grapes, depending on the environment → Sectoring is common in culture → Sclerotia may be formed in old cultures → Long, branching, olive-grey, aerial conidiophores with swolen apical cells that are covered with ovoid conidia borne on short projections

SPECIES: → A collection of strains that exibit many common characteristics and which differ from other strains. STRAIN: → Descendants of a single cell/isolate (clones). TYPE STRAIN: → A reference specimen that typifies the species.

LYTIC: virus kills infected cell LYSOGENIC: virus genome is integrated into host genome (infection remains latent)

→ Food spoilage, plant diseases → Some produce mycotoxins → Form dense, powdery colonies → Typically grey, green, or bluish, with a white margin where conidia haven’t formed yet → Characteristic brush-like conidiophore (the penicillus) with chains of conidia → Species can be distinguished based on the morphology of the penicillus and the size, shape, and colour of the spores.

20-300 nm longest = 2000 nm Multiple shapes.

• Virions enter the cytoplasm of a living cell • Virus genes expressed in host cell • New virions assemble from viral RNA/DNA and protein • Virions escape the cell and infect new cells • Infected host cells show disease

A set of one or more genomic nucleic acid molecules, normally encased in a coat/s of protein or lipoprotein, that is able to replicate itself within suitable host cells.

False. They also infect bacteria, algae, and protozoa. That said, each virus has individual host-specificity.

CLASSIFICATION: → Arranging organisms into taxonomic groups based on similarities or relationships IDENTIFICATION: → Determining that a new isolate belongs to an established taxonomic group

HORIZONTAL: → Between individual hosts of the same generation - aerosols - ingestion - contact - tissue transfer - vector (e.g. mosquito) VERTICAL: → From parent to offspring - milk - placenta - seed - integrated into parent genome

True.

→ Common pathogens of aerial plant parts, often causing leaf and pod spots → Dark gray/black colonies → Often form concentric zone lines (dark areas where conidia are dense) → Characteristic large, multicellular, darkly coloured conidia borne on simple, pigmented conidiophores. → Best viewed without stain (lactoglycerol only)

Small, circular RNA molecules that can infect PLANT CELLS, replicate themselves, and cause PLANT disease.

SIZE: Generally 20-300 nm in diameter SHAPE: sphere, rod, bullet, lemon, tailed STABILITY: varying sensitivity to temp, pH, salt, radiation, desiccation, enzymes, etc