MI01: Microbes and the Microbiome Flashcards

Vocabulary flashcards covering key concepts of microbes, bacterial cell structure, biofilms, and the microbiome based on lecture slides.

Prokaryotes

Unicellular organisms that do not have a membrane-bound nucleus, mitochondria, chloroplasts, or other membrane-bound organelles, including bacteria and archaea.

Eukaryotes

Organisms whose cells contain a membrane-bound nucleus, which may be unicellular or multicellular, including protists, fungi, and helminths.

Acellular Infectious Agents

Infectious agents lacking cellular structure, consisting of viruses, viroids, and prions.

Pathogen

A microbe capable of causing host damage.

Extracellular Pathogen

A pathogen that causes damage while outside of host cells.

Intracellular Pathogen

A pathogen that must be inside host cells to cause damage.

Iceberg Concept of Disease

A framework describing that most microbial encounters are prevented by barriers or resolved subclinically by the immune system, with severe disease or death representing the rarest outcome.

Cocci

Sphere-shaped eubacteria.

Bacilli

Rod-shaped eubacteria.

Capsule

A polysaccharide layer outside the cell envelope of some bacteria that protects from toxins, desiccation, and phagocytic engulfment, while aiding attachment and increasing virulence.

Flagella

Bacterial appendages that act as organs of movement, allowing bacteria to move via chemotaxis towards a stimulus.

Fimbriae and Pili

Thin, hair-like bacterial surface appendages involved in attachment; pili are involved in bacterial conjugation, while fimbriae are shorter and more numerous.

Peptidoglycan

A polymerized network mesh unique to bacterial cell walls that holds the cell together, acts as a Microbial-Associated Molecular Pattern (MAMP), and is targeted by lysozyme and penicillin antibiotics.

Gram-Negative Cell Envelope

A bacterial cell envelope composed of a thin peptidoglycan layer, an inner membrane, and an outer membrane containing lipopolysaccharide (LPS) and porins.

Gram-Positive Cell Envelope

A bacterial cell envelope composed of a thick peptidoglycan layer and an inner membrane only.

Lipopolysaccharide (LPS)

An endotoxin on the outer membrane of Gram-negative bacteria that acts as a powerful immune activator, whose Lipid A core release during lysis can trigger fever, diarrhea, and septic shock.

Plasmids

Small, extrachromosomal DNAs in bacteria that code for nonessential information, replicate independently of the chromosome, and can be transferred between bacteria.

Endospores

Dormant structures formed by certain Gram-positive bacteria to survive harsh conditions, protected by small acid-soluble proteins (SASPs), dipicolinic acid complexed with calcium (Ca-DPA), and outer membrane and spore coats.

Archaea

Prokaryotes evolutionarily distinct from bacteria that share metabolic pathways with eukaryotes, inhabit extreme environments, and have no known human pathogens.

Fungi

Eukaryotic organisms, including yeasts and molds, that contain chitin in their cell walls and include over 300 known human pathogens.

Helminths

Multicellular, worm-like parasites—including flukes, tapeworms, and roundworms—that infect nearly 2,000,000,000 people worldwide.

Protozoa

Single-celled, motile eukaryotic parasites that cause severe human diseases such as malaria.

Viruses

Obligate intracellular parasites with DNA or RNA genomes encased in a protein coating that utilize host cell ribosomes to replicate.

Viroids

Infectious pathogens composed of small single-stranded, circular RNAs that lack a protein coating and do not encode proteins.

Prions

Misfolded proteins that induce misfolding in normal variants of the same protein, causing cellular death, and are resistant to proteases, heat, ionizing radiation, and formaldehyde.

Biofilm

Clusters of microorganisms sticking to biological or non-biological surfaces, often encased in a self-produced or host-derived polymer matrix.

Ultramicrobacteria

A shrunken, spore-like bacterial state induced by starvation, allowing cells to wait in water, soil, rock, or tissue until conditions permit active growth.

Microbiota

The living organisms found in a defined environment.

Microbiome

The collection of genomes from all the microorganisms in a defined environment.

Operational Taxonomic Units (OTUs)

A count of microbial species or predicted species based on 16S rRNA sequencing.

Dysbiosis

A disruption or shift from a healthy microbiome to an abnormal microbiome state associated with disease.

Ocular Surface Microbiome Core

The main resident microbiota of the ocular surface, predominantly consisting of coagulase-negative Staphylococcus (CNS), Cutibacterium, and Corynebacterium.