VM500 MIcrobiology and Virology

Prokaryotic Cell

no nucleus, genetic material is within the cytosol in a single circular chromosome (usually), lack membrane-bound organelles, 70S ribosome, cell wall with peptidoglycan, cell division via binary fission

Bacterial Taxonomy

classification of organisms based on phenotypic and phylogenic traits, fundamental unit is the species

Peptidoglycan

unique and cross-linked macromolecule that forms a net around the cell giving it structure, acts as a course sieve for the bacterium, made of NAM and NAG subunits linked together, peptide cross-linking is characteristic of gram positive bacteria

Bactoprenol Carrier Lipid

transports NAM-NAG-peptide building block of peptidoglycan outside the cell from the cytosol

Gram Positive

thick cell wall of peptidoglycan, anchored to the cytoplasmic membrane by lipoteichoic acid, covalently linked to teichoic acid

Teichoic Acid

unique to gram positive bacteria, polymer of glycerol phosphate or ribitol phosphate to sugars, amino acids, and other molecules can be attached as well

Gram Negative

has a thin cell wall with a periplasmic space and an outermembrane with lipopolysaccharides (LPS) and porins

Periplasmic Space

region between inner and outer membranes, contains hydrolytic enzymes, binding proteins, and peptidoglycan biosynthetic enzymes

Outer Membrane

only present on gram negative bacteria, contains LPS

Lipopolysaccharide

only found in gram negative bacteria in the outer membrane, lipid A portion is extremely toxic and can cause endotoxic shock, major virulence factor, composed of lipid A, core polysaccharide, and repeating O antigen

Capsule

loose, relatively unstructured hydrophilic layer around a bacteria that prevents desiccation and development of an immune response, usually antigenic but not toxic

Flagella

long helical protein filaments that enable bacterial motility and chemotaxis, can be important surface antigens, found on both gram negative and positive

Pili/Fimbriae

hair-like protein projections on bacterial surface, often attach to host cell

Cell Membrane

phospholipid bilayer with embedded proteins and is selectively permeable, generates energy via ETC

General Secretion Pathway

secreted proteins have N-terminal signal sequence that is cleaved by signal peptidase, extracellular secretion in gram negative bacteria requires more complex machinery to bypass outer membrane

Chemoheteroptroph

gets energy from oxidizing an organic compound, and its carbon source is organic

Chemoautotroph

energy course comes from the oxidation of inorganic substances and the carbon source is CO2

Photoheterotroph

uses light as an energy source and an organic carbon source

Photoautotroph

uses light as an energy source and CO2 as a carbon source

Nutritional Immunity

the general withholding of necessary elements from bacteria by infected hosts

Respiration

re-oxidation of reduced molecules generated during the fueling pathway, relies on ETC to a terminal acceptor, ATP generated by substrate level phosphorylation and oxidative phosphorylation

Fermentation

re-oxidation of reduced molecules from fueling pathways done directly by reducing organic metabolites, involves organic electron donors and acceptors, does not require oxygen or ETC, only generates ATP by substrate-level phosphorylation

Strict Aerobes

require oxygen to generate by respiration, use oxidative metabolism and cannot ferment, possess catalase and superoxide dismutase

Strict Anaerobes

grow in the absence of oxygen and vary in sensitivity to oxygen, get energy via fermentation, does not usually possess catalase or SOD, but some may have SOD

Facultative Anaerobes

respire in the presence of oxygen, ferment in its absence, usually have both catalase and SOD

Auxotrophs

bacteria with enzymes or pathways missing, can not make all of its own essential compounds, need the molecule provided to them because it cannot be made by the bacterium

Type I Viral Genome

Double stranded DNA viruses

Type II Viral Genome

-ssDNA viruses

Type III Viral Genome

Double stranded RNA viruses

Type IV Viral Genome

+ssRNA → mRNA

Type V Viral Genome

-ssRNA

Type VI Viral Genome

+ssRNA → ds DNA (retroviruses)

Type VII Viral Genome

Partially dsDNA, segments may be missing

dsDNA Genome

Can be directly transcribed and replicated, can be circular or have looped ends to preserve genome length, herpes and adeno virus

ssDNA Genomes

Converted to dsDNA in the host for transcription and replication, can have many genome forms (circular, looped), parvo virus

Positive ssRNA Genome

can be directly translated by ribosome and must convert to negative sense to replicate, usually linear, coronavirus

dsRNA Genome

can be directly translated and replicated, can be segmented, reovirus

Negative ssRNA Genome

Must be converted to positive sense for replication and translation, can have segmented genomes or not, rabies

Retrovirus

A ssRNA that has a DNA intermediate that is integrated into the host genome as a provirus

Monopartite

Virus with their genome in a single piece (non segmented)

Recombination

Occurs in a coinfected cell when two viruses get their genome mixed together on the same nonsegmented genome

Reassessment

Occurs with segmented RNA viruses in a coinfected cell when different pieces of both genomes are packaged into the same virion

Viral Genome Function

Encode minimal information for genome replication, encoding information for the production of viral proteins, and subversion of cellular functions

Capsid

Outer layer of a virion encapsulating the viral genome, can be icosahedral, helical, or complex

Tegument

Protein layer between the capsid and the envelope in an enveloped virus

Envelope Glycoproteins

Mediate interactions between virions and cells, major target of neutralizing antibodies

Viral Replication Cycle

Attachment via adhesion receptors and entry receptors, entry via fusion and receptor mediated endocytosis, penetration, replication, and egress

Receptor Mediated Endocytosis

Viral binding to a surface receptor triggers internalization of the receptor into an acidic endosome, low pH triggers viral protein changes and viral membrane fuses with endsome to release into cytosol

RNA-dependent RNA Polymerase (RdRP)

Necessary viral protein that aids all RNA viruses (except retroviruses) to replicate their genome and produce their mRNA

Firmicutes

first type of bacteria to colonize an infant, specifically lactobacilli

Proteobacteria

second group of bacteria to be introduced to a baby, some exposure to pathogens is normal in this stage

Bacteroidetes

class of microbe that increases once solid food is introduced to a baby, gets more enriched and diverse in microbiota as the baby reaches toddler age

Microbiota Impact on Development

development and differentiation of mucosal epithelium, development of immune functions, development of nutritional capabilities, provision of nutrients, detoxification of harmful dietary constituents, and colonization resistance

Colonization Resistance

commensal microbiota protects against pathogens by occupying adhesion sites, altering physiochemical environment, producing antagonistic substances, and utilizing available nutrients

Transfaunation

aka fecal transplant, ruminal fluid transfer by oral transfer from a normal animal that has rumen bacteria, protozoa, and VFAs

Protozoa

eukaryotic organisms that are typically unicellular, lack cell walls, vary widely in size and structure, and are mostly motile heterotrophs

Ciliates

have cilia present at some stage of the life cycle, a macro and micronucleus, commensals in ruminants that make up 50% of the microbial mass

Flagellates

use a flagella as locomotion or food-capturing organelle, as a commensal it is important for enhancing immune response by promoting Th1 and 17 to mount an antibacterial defense

Amoebas

use pseudopodia for locomotion and highly structured skeletal interior, usually pathobiont and can lead to death

Apicomplexas

ring-like, tubular, and filamentous organelles at the apical end, bore into cells in a spinning motion

Balantidium coli

ciliate pathogenic protozoa that has cyst and trophozoite life cycle, pigs are a major reservoir and are asymptomatic, causes a form of dysentary

Tritrichomonas

a flagellate protozoa that enhances anti-bacterial response in the gut of mammals, aids in colonization resistance by releasing antibacterial compounds

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