6. Legionella

What severe disease is caused by Legionella

Legionnaires Disease

Legionnaires disease

Severe pneumonia

What less severe disease is caused by legionella

Pontiac fever

Pontiac fever

Less severe respiratory like illness

Legionella transmission

Normally aerosolized droplets from untreated water

Legionella pneumophila gram stain

Gram negative

L. Pneumophila oxygen requirements

Aerobic

L. Pnuemophila motility

Only has flagella when EXTRACELLULAR

L. Pneumophila replication

Intracellular replication once inside host

L. Pneumophila- amoebas

Amoebas try to eat it and it survive INSIDE amoeba

L. Pneumophila flagella

Crucial for dispersing in the lungs of patients, but not expressed once inside host or amoeba

Legionella pili

Fimbriae involved in binding to host cells

Legionella LPS

Aids in host attachment

Legionella MIP- (macrophage infectivity
potentiator)

Required for early intracellular infection

Legionella MOMP- (major outer membrane
protein)

Porin properties to facilitate adherence and entry into host cell or amoeba

What type of host cell can legionella survive in

Macrophages

First step of legionella survival in macrophages

Enters via phagocytosis

Second step of legionella survival in macrophages

Biohacking

3rd step of legionella survival in macrophages

Avoids lysosomal fusion to form legionella-containing vacuole (LCV)

4th step of legionella survival in macrophages

Inside LCV replication occurs, then flagellation to escape and continue infection

Biohacking

Recruits mitochondria, ribosomes, and smooth ER vesicles to surface of endosome to steal energy and nutrients

LCV

Vacuole inside macrophage where legionella happily reproduces

Bacterial secretion systems

Used by bacteria to secrete virulence factors

T1 secretion system (T1SS) in legionella

IssB/IssD

IssB/IssD

Regulates expression and export of RtxA toxin which forms pres in host cells to induce Ca ion release

RtxA

Toxin required for adhesion and entry into host cells and amoebas because it creates pore in host cells

T2SS in legionella

Lsp SS

Lsp type 2 SS

Legionella secretion pathway which secretes over 25 effector proteins involved in pathogenesis

Legionella t4SS

Dot/Icm

Dot/Icm T4SS

Secretes over 300 effectors out of the LCV into the host cytoplasm

CRUCIAL FOR LCV SURVIVAL

How is the release of effector proteins from Dot/Lcm T4SS regulated

By signaling molecule c-di-GMP

Cyclic-di-GMP

Signaling molecule that is tightly regulated since it controls many virulence factors

Cyclic-di-GMP production

By diguanylate cyclases with GGDEF amino acid motifs

Diguanylate cyclase must have what motif for c-di-GMP production

GGDEF

Cyclic-di-GMP degradation

By phosphodiesterase with EAL or HD-HYP amino acid motifs

Which motif is needed for c-di-GMP degradation by phosphodiesterase

EAL or HD-GYP

PilZ bound to c-di-GMP

Inhibits motility and virulence while increasing factors required for biofilms

Legionella biofilms

Bacterial communities either alone or with other bacteria in WATER PIPES

Legionella quorum sensing

Allows bacteria to regulate gene expression in density-dependent manner

When they are free floating, is c-di-GMP high or low

Low because they want virulence factors and motility here

High c-di-GMP

Associated with biofilm formation, and repressed virulence and motility

Why would legionella want to survive in an amoeba

Similar to biofilms, where bacteria are protected from antibiotics, high temps, and disinfectants

Also amoebas move to transport bacteria