CLASSIFICATION OF MICROORGANISMS

DISCLOSURE Relevant relationships with commercial entities none Potential for conflicts of interest within this presentation none Steps taken to review and mitigate potential bias N/A

LEARNING OBJECTIVES This lecture is designed to meet the following end-of-week learning objective: 1. Describe the broad group classification of microorganisms and the differences between bacteria, fungi, viruses, and parasites 2. Describe the classification of bacteria and fungi.

MODULE OBJECTIVES By the end of this module, you should be able to: 1. Describe a general scheme to classifying microorganisms 2. Differentiate the major different classes of microorganisms 3. Identify where common/important microorganisms (highlighted in this lecture) fit into the classification scheme

RECOMMENDED READING Engleberg et al (eds.) Schaechter s Mechanisms of Microbial Disease (5th Edition), Lippincott Williams & Wilkins 2013 - Chapters 10, 31, 46, 51

GENERAL DEFINITIONS Microorganisms an organism (form of life) of microscopic or submicroscopic size Microbiology the branch of biology that deals with microorganisms and their effects on other living organisms Medical Microbiology the branch of medicine that deals with microorganisms and their effects on human health

GENERAL CLASSIFICATION Microorganisms Bacteria Viruses Fungi Parasites (Ch. 10) (Ch. 31) (Ch. 46) (Ch. 51)

RELATIVE SIZE OF MICROORGANISMS Limits of Resolution: 50,000-V electron microscope 0.003 m Light microscope 0.2 m Unaided human eye 40 m Bacteria 0.1-10 m Viruses 0.03-0.3 m Protozoa & Fungi 4-40 m 0.001 0.01 0.1 1 10 100 Size ( m)

BACTERIA - DESCRIPTION Prokaryotic, single cell organisms characterized by the presence of a strong cell wall containing peptidoglycan single circular chromosome absence of a distinct, membrane-bound nucleus absence of membrane-bound organelles divides by binary fission

Bacterial Cell Structure Black JG. Microbiology Principles and Explorations 5 th Edition 2002

Binary Fission Black JG. Microbiology Principles and Explorations 5 th Edition 2002 Slide 11

BACTERIA - CLASSIFICATION Divided into Gram-positive and Gramnegative Divide by microscopic morphology Divided into aerobic and anaerobic based on whether they can tolerate environments with oxygen

BACTERIA - EXAMPLES O 2 Staphylococcus spp. Listeria spp. Neisseria spp. E. coli Streptococcus spp. Corynebacterium spp. Moraxella spp. P. aeruginosa Enterococcus spp. Bacillus spp. [Haemophilus spp. (coccobacilli)] AnO 2 Peptostrepto- Clostridium spp. Veillonella spp. Bacteroides spp. coccus spp.

VIRUSES - DESCRIPTION Acellular infectious particles consisting of a core of RNA or DNA surrounded by a protein coat (capsid), unable to replicate without a host cell

Viral Structures Black JG. Microbiology Principles and Explorations 5 th Edition 2002

Viral Replication Black JG. Microbiology Principles and Explorations 5 th Edition 2002 Slide 18

Black JG. Microbiology Principles and Explorations 5 th Edition 2002

VIRUSES - CLASSIFICATION Divided into DNA vs. RNA viruses Sub-divided by: single-stranded, double-stranded, segmented nucleic acid presence/absence of envelope shape of capsid icosahedral (20 faces), helical, complex

VIRUSES - EXAMPLES Viruses DNA Hepatitis B Herpesviruses Adenovirus Parvovirus B19 Poxviruses RNA Hepatitis A, C, E, G Influenza A, B Respiratory Syncytial Virus HIV West Nile Virus Rotavirus Norovirus

FUNGI - DESCRIPTION Eukaryotic, uni- to multi-cellular organisms characterized by the presence of a rigid cell wall predominantly made of chitin, mannan, and glucan that can reproduce asexually or sexually

Fungal Cell Structure plasma membrane & cell wall nucleus mitochondria microtubules

FUNGI - CLASSIFICATION Divided into yeast and filamentous fungi (the latter also referred to as moulds)

Single cells, ovoid or spherical Divide by budding YEAST

FILAMENTOUS FUNGI (MOULDS) Multi-cellular Grow as microscopic, branching, threadlike filaments (hyphae), collectively known as mycelium

FILAMENTOUS FUNGI (MOULDS) Multi-cellular Grow as microscopic, branching, threadlike filaments (hyphae), collectively known as mycelium Black JG. Microbiology Principles and Explorations 5 th Edition 2002

FUNGI - EXAMPLES Fungi Yeast Moulds Candida spp. Cryptococcus neoformans Aspergillus spp. Histoplasma capsulatum Blastomyces dermatitidis Zygomycetes

PARASITES - CLASSIFICATION Eukaryotic, uni- to multi-cellular organisms that live upon or within another living organism

PARASITES - CLASSIFICATION Divided into protozoa and helminths

PROTOZOA One-celled eukaryotes bounded by only a cell membrane that reproduce asexually and sexually Divided into categories Amoebae, ciliates, flagellates, coccidia, microsporidia, sporozoa Divided by typical site of infection Intestinal, blood, tissue, other

HELMINTHS (WORMS) Multicellular eukaryotic organisms that reproduce sexually Divided into categories Nematodes (round worms), cestodes (flat worms), trematodes (flukes) Divided by typical site of infection Intestinal, blood, tissue

PARASITES EXAMPLES Parasites Protozoa Helminths Intestinal Entamoeba histolytica Ascaris lumbricoides Giardia lamblia Taenia spp. Blood Plasmodium spp. Schistosoma spp. Other Sites Toxoplasma gondii Acanthamoeba spp. Echinococcus spp.

QUIZ What are the four main classes of microorganisms?

QUIZ What are the four main classes of microorganisms? 1. Bacteria 2. Viruses 3. Fungi 4. Parasites

KEY MESSAGES Microorganisms can be classified as follows: 1. Bacteria Gram-Positive vs Gram-Negative Cocci or Bacilli Aerobic vs. Anaerobic 2. Viruses DNA vs RNA 3. Fungi Yeast vs filamentous fungi (moulds) 4. Parasites Protozoa vs. Helminths

MODULE OBJECTIVES By now you should be able to: 1. Describe a general scheme to classifying microorganisms 2. Differentiate the major different classes of microorganisms 3. Identify where common/important microorganisms (highlighted in this lecture) fit into the classification scheme