Vibrio

gram stain of vibrio spp.

gram-negative

shape of vibrio spp.

curved rods

motility of vibrio spp?

motile; usually possess a single polar flagellum

Vibrio genera: what kinds of environments do they thrive in?

halophilic marine microbes; usually found in seawater; ass. with contaminated seafood or water

highest concentration of NaCl that vibrio spp can tolerate?

18%

at what pH do vibrio spp grow

neutral to alkaline pH

optimum pH for vibrio spp

8.8

What pH condition are vibrio spp sensitive to?

acidic

temperature vibrio spp grow at

20-37C

what is unique about the genome of vibrio spp

it is split between two chromosomes; MOST BACTERIA ONLY HAVE ONE CHROMOSOME

How is the genetic informaiton divided between the two vibrio chromosomes

one contains most essential information and the other contains species-specific virulence factors

which pathogenic vibrio spp does not require high salt envrionments

vibrio cholerae

What pathogenic vibrio species (that we discussed in class) requireds high salt concentrations

Vibrio vulnificans

what structure to vibrio communities form

biofilms

what is vibrio pathogenic behavior regulated by

Quorum sensing and an “odd” two component system

What are the vibrio autoinducer molecules

HAI-1, CAI-1, and AI-2

what genes are the vibrio autoinducer molecules produced from

LuxM, CqsA, and LuxS

What do the vibrio autoinducer molecules bind to

membrane-bound histidine kinase receptors LuxN, CqsS, and LuxPQ

what is the action of the membrane-bound autoinducer receptors (LuxN, CqsS, and LuxPQ) when concentrations of autoinducer are low

the receptors are unbound, and the receptors act as kinases to phosphorylate LuxU

LuxU

the phosphotransfer protein

What is the function of LuxU

When the receptors are unbound (resulting in phosphorylated LuxU), LuxU phosphorylates LuxO

LuxO

the response regulator

What happens when there is little autoinducer present and LuxO ends up phosphorylated by LuxU?

Together with Sigma-54, it activates expression of the 5 WRRs

what happens when there is little autoinducer present and LuxO, the response regulator has activated the expression of the 5 QRRs?

LuxR translation is repressed and AlphaA translation is activated

What happens when having little autoinducer around leads to LuxR translation repression and AphA translation activation?

the expression of genes for individual behaviors

What transcription factor activates and represses certain genes in order to achieve the best group behavior activities

LuxR

When is LuxR activated

when there is lots of autoinducer/NO present to bind the receptors and turn them into phosphotases

what happens as a result of high amounts of autoinducers binding to the receptors?

the receptors are turned into phosphatases rather than kinases. This results in dephosphorylated LuxOand lack of Qrr expression. Therefore, the expression of LuxR is maximal.

what are autoinducers?

organic molecules that are used for signaling how many bacteria are present in the surrounding area

In autoinducer sensing, when is the response regulator phosphorylated?

when the receptors are not bound to their signal

cholera toxin molecular function

ADP-ribosylates GSA protein, activating adenylate cyclase

effect of cholera toxin on the host

causes severe, watery diarrhea, leading to dehydration

species associated with cholera toxin

vibrio cholerase

hypothesized origin of the cholera toxin

phage (CTXφ lysogenic phage)

Cholera toxin mechanism of secretion

Type II secretion

RTX toxin molecular function

multifunctional, cytolytic toxin affecting actin dynamics

effect of RTX toxin on host

cytotoxicity to immune and epithelial cells

RTX species

vibrio vulnificans

hypothesized origin of RTX toxin

chromosomal

RTX toxin mechanism of secretion

Type I secretion system

MARTX toxin mechanism of action

inactivates RHo GTPases and disrupts cytoskeleton

effect of MARTX toxin on human host

cell rounding, apoptosis, and immune evasion

Zonula occludens toxin mechanism of action

disrupts tight junctions between epithelial cells

effect of zonula occludens toxin on the host

increased intestinal permeability

species associated with zonula occludens toxin

vibrio cholerae

hypothesized origin for zonula occludens toxin

CTXφ lysogenic phage

mechanism of secretion of zonula occludens toxin

Type II SS

heat-stable enterotoxin mechanism of action

activates guanylate cyclase, increasing cGMP levels

effect of heat-stable enterotoxin on host

diarrhea due to electrolyte imbalance

species associated with heat-stable enterotoxin

vibrio cholerae

mechanism of secretion of heat-stable enterotoxin

Type II secretion system

what did Filippo Pacini do (with relation to cholera)

discovered Vibro cholera; did not know that it came from contaminated water; was really good with the microscope and took really good notes describing the bacteria

What did John Snow do (with relation to cholera)

described the method of cholera spread; Broad street pump

What did Robert Koch do (with relation to cholera)

isolated the organism in pure culture

in nature, where is vibrio cholerae almost always found

in freshwater and estuarine ecosystems where it forms biofilms and associates with zooplankton

what are the epidemic serogroups of vibrio cholerae

O1 and O139

typical O1 serogroup capsule status

no capsule

typical O139 serogroup capsule status

usually capsule

how many cholera epidemics have there been since 1817

7, with the 7th ongoing

transmission source of cholera

contaminated water and food (usually contaminated with feces)

how does the contagiousness of cholera compare with that of other bacteria?

way more contagious

what part of the body does vibrio cholerae colonize

the small intestine epithelial cells

In the body, what does vibrio cholerae adhere to and what does it do when it adheres here?

the intestinal lining where it releases toxins that disrupt the fluid balance, causing severe diarrhea an ddehydration

what are the symptoms of vibrio cholerae

profuse, watery diarrhea and dehydration; “rice-water stool”

mortality of cholera

untreated cholera results in high mortality due to rapid fluid loss, severe dehydration, hypovolemic shock, and death within hours

what are the serogroup classifications of cholera usually based on?

based on the O-antien of LPS

what is the key feature present in epidemic strains of cholera

they produce cholera toxin

what is the virulence in serogroup O1 mostly driven by?

acquisition of mobile genetic elements including bacteriophages, genomic islands, and conjunctive elements

what is the Biotype within serogroup O1 that is currently causing a pandemic

El Tor

what are the cholera biotypes within serogroup O1

El Tor and Classical

what is the difference between the Classical and El Tor biotypes in the O1 serogroup

the phages that infected them and what pathogenicity islands were delivered

VPI-1 pathogenicity island

encodes key virulence factors in vibrio cholerae

What virulence factors does the VP1 pathogenicity island encode?

toxin-coregulated pilus (TCP), which is essential for small intestine colonization and this is also used as a receptor for the CTXφ bacteriophage

What is needed to the CTXφ bacteriophage to infect vibrio cholerae

the toxin-coregulated pilus which is encoded by the VPI-1 pathogenicity island

is VPI-1 always stuck in the chromosome?

No, it can excise from the chromosome, forming a circular extrachromosomal product, indicating potential transferability

TCP

toxin co-regulated pilus

What type of pilus is the TCP?

Type IV pilus

What are the important functions of TCP

helps V. cholerae attach to and colonize the intestinal lining, facilitates the formation of microcolonies that promote colonization, and serves as the receptor for CTXφ

what is the structure of the cholera toxin

AB5 structure

how does the AB5 toxin interact with the host cell

B subunits bind GM1 receptor → the AB toxin is internalized into an endosome → vesicle mediated transport as it needs to get to the ER for AB to separate → A and B separate → A becomes activated by ARF6 → the activated A subunit activates adenyl cyclase → lots of cAMP production → activation of protein kinase A → phosphorylated CFTR channels → lead to the release of electrolytes and water into the intestinal lumen, causing secretory diarrhea

where does the cholera toxin need to go for the A and B subunits to separate

the ER

What does the activated A subunit of cholera toxin do?

activates adenylyl cyclase to produce a lot of cAMP and phosphorylate protein kinase A

After protein kinase A becomes phosphorylated as a result of the A subunit of cholera toxin, what happens?

the CFTR channel becomes phosphorylated, leading to the efflux of electrolytes and water into the ER lumen

what does ZOT bind to

zonulin receptor triggering intracellular signalling pathways, specifically protein kinase C

what happens when protein kinase C is activated by ZOT

phosphorylation and destabilization of the actin cytoskeleton, weakening connections between tight junctino proteins, increasing paracellular permeability

what does the increased permeability as a result of the ZOT toxin result in

leakage of ions and water into the intestinal lumen, causing diarrhea and water loss

What causes the intestinal “swiss-cheesing” associated with vibrio cholera?

Zonula occludens toxin

what is the primary treatment for vibrio cholera

rehydration therapy salts/intravenous fluids

where is vibrio vulnificans found in the environment

warm, coastal waters as this is a halophilic bacterium

what is vibrio vulnificus known for

the “flesh-eating bacteria” that has rapid disease progression and high virulence

how is vibrio vulnificus most commonly transmitted?

raw seafood or open wounds

what are the three types of infections caused by vibrio vulnificus

• acute gastroenteritis

• necrotizing wound infections

• invasive sepsis

what do necrotizing wound infections involve (V. vulnificus)

involves pre-existing cut or skin lesion that gets colonized

Describe invasive sepsis that can result from vibrio vulnificus

Systemic disease: bact. invade intestinal tract, then translocate to the blood stream, where it proliferates causing septicemia. Once in blood, it can get to the cutaneous tissue and cause edematous hemorrhagic skin lesions, septic shock, and death.

what is the structure of the (Ma)RTX toxin

can contain multiple subunits that can act on specific host targets such as inactivating Rho GTPases and targeting other factors resulting in the disruption of actin, cell rounding, and apoptosis

what toxin of Vibrio vulnificus is responsible for most of the damage caused by this bacterium

the (MA)RTX toxin

how does the (MA)RTX first interact with the host

the toxin is secreted via an atypical T1SS → the toxin forms a pore in the host cell PM → the subunits get in and cause their problems

how is a vibrio vulnificus infection treated/

• immediate treatment with doxycycline and a third generation cephalosporin

• wound care (debridement or amputation)

• managing sepsis

If the vibrio vulnificus infection is cleared by antibotics, why do limbs sometimes have to be amputed?

the toxins secreted by the bacteria are left behind even when the bacteria is cleared