1 Mycology Introduction Mycology The study of fungi Fungi are eukaryotic heterotrophic and unicellular to filamentous rigid cell walled spore bearing organisms that usually reproduce by both sexual and asexual means Further they are insensitive to antibacterial antibiotics Probable questions I How do you Classify fungi based on morphology 1 Yeast a Unicellular fungi b Reproduce asexually by budding to form blastoconidia c Macroscopic appearence Bacteria like moist smooth creamy colonies d Microscopic appearance Single round to oval budding cells Example Cryptococcus neoformans 2 Yeast like a Unicellular fungi b Reproduce asexually by budding to form blastoconidia c Macroscopic appearence Bacteria like moist smooth creamy colonies d Microscopic appearance Single round to oval cells e Presence of Pseudohyphae Example Candida spp f Pseudohyphae Elongation of blastoconidia showing sausage like constrictions between segments true hyphae are not constricted at ends 3 Mould a Reproduce either asexually vegetative sporulation or aerial sporulation or sexually sexual sporulation b Macroscopic appearance Surface texture may be cottony veletty wooly or granular Pigmentation may be observed from the reverse Growth of hyphae 2 which form a matt of growth called the mycelium c Microscopic appearance Thread like filamentous hyphae which may be septate with cross walls or aspetate without cross walls Multiple cells forming a filamentous mycelium Example Aspergillus spp Dermatophytes Mucor 4 Dimorphic fungi phase a Fungi that have the ability to exist in two forms depending on growth conditions b Generally dimorphic fungi have a mould phase and either a yeast or spherule Yeast tissue phase grows in culture at 37o C and in tissues Mould phase grows best at room temperature or 22o 25oC and in environment Example Histoplasma capsulatum 5 Structures Hyphae a Long strand of tube like structures b Types Aseptate Septate Aseptate hyphae Septate hyphae Without cross walls With cross walls 3 Mycelium Mass of branching intertwined hyphae forming a matt of growth Types a Aerial mycelium also called reproductive mycelium o Portion of mycelium that projects above the agar CONIDIA surface b Vegetative mycelium and nutrient o Extends into substratum of agar and is responsible for absorbing water II Culture Media for fungal isolations a Sabroud s dextrose agar Commonly used media SDA is a selective medium primarily used for the isolation of Fungi The acidic pH of this medium pH about 5 4 inhibits the growth of bacteria but permits the growth of fungi Antibiotics like Chloramphenicol Gentamicin and Tetracycline can be added as selective agents to inhibit bacterial overgrowth while permitting the successful isolation of fungi and yeasts b Czapek Dox medium c Dermatophyte test medium d Bird seed agar e Corn meal agar f Chromogenic agar CHROM agar different species of Candida produce different coloured colonies III OPPURTUNUSTIC FUNGI It is a filamentous fungus 1 Aspergillus flavus Macroscopic features On SDA Obverse Colonies are granular flat yellow at first but quickly becoming bright to dark yellow green with age 4 Reverse Yellow Microscopic features a Septate Hyphae b Colorless rough conidiophores c Biseriate or uniseriate Phialides d Round radiate head Vesicle e Phialides surround the whole vesicle 2 Aspergillus fumigatus It is Filamentous Fungi Macroscopic Morphology On SDA Obverse Colonies are velvety or powdery at first turning to smoky green Reverse Green Microscopic Morphology a Septate hyphae b Conidial heads are typically columnar and uniseriate c Conidiophores are short smooth walled and have conical shaped terminal vesicles which support a single row of phialides on the upper two thirds of the vesicle 5 3 Aspergillus niger It is a Filamentous Fungi Macroscopic features on SDA Obverse colonies are woolly yellow at first later turning black Reverse black Microscopic Morphology a Conidial heads are large globose dark brown b Conidial heads are biseriate c Conidiophores are smooth walled MACROSCOPIC MICROSCOPIC FEATURES OF ASPERGILLUS SPECIES SPECIES A flavus A fumigatus A niger 6 SURFACE Obverse side Yellow green Blue green to gray Black REVERSE to red White to tan White to yellow Goldish brown CONIDIOPHORE Colorless rough Short 300 m smooth colorless or greenish Long smooth colorless or brown PHIALIDES Uni biseriate Covers the whole vesicle Uniseriate Covers the upper 1 3rd of the vesicle Biseriate Covers the whole vesicle VESICLE Round head radiate columnar Round head Covers the whole vesicle 4 Penicillium species 7 Is a Filamentous Fungi Microscopic features Macroscopic Morphology on SDA colonies are blue green in colour with a white border and a powdery surface a Hyphae hyaline septate and multibranched b Conidiospore arise in various forms producing phialide c Phialides single or in groups or form branched metulae giving brush like appearance Human infections Causes Otomycosis and Keratomycosis The only Pathogenic species is Penicillium marneffi It s an opportunistic pathogen in HIV patients 5 Mucor Mucor is a filamentous fungus common laboratory contaminant Macroscopic Features On SDA Obverse Fluffy appearance the color is white initially and becomes grayish brown in time Reverse it is white Microscopic Features a Nonseptate hyphae 8 b Sporangiophores are long branched and bear large round sporangia c Sporangia are round gray to black in color and are filled with sporangiospores d The sporangiospores are round e No rhizoids are formed Infection caused by Mucor mucocutaneous and rhino cerebral infections septic arthritis dialysis associated peritonitis renal infections gastritis and pulmonary infections Rhizopus is a filamentous fungus common laboratory contaminant 6 Rhizopus Macroscopic Features On SDA Obverse The color of the colony is white initially and turns grey Reverse white to pale Microscopic Features a Nonseptate aseptate hyphae b Sporangiophores are brown in color and usually unbranched c Rhizoids root like hyphae are located at the point where the stolons and d Sporangia are located at the tip of the sporangiophores They are round with sporangiophores meet flattened bases 9 e Sporangiospores are unicellular round to ovoid in shape hyaline to brown in color f Rhizopus species illustrating sporangium sporangiophore sporangiospores coenocytic hyphae andrhizoids Human Infections Causes Oppotunistic infection in immunocompromised patients uncontrolled Diabetes mellitus like rhinocerebral