A Microbial Moment

Bio 254 Microbiology:Bacteria and Viruses

 

brought to you by Christine White-Ziegler

 

 

Name of bacterium (genus and species): Escherichia coli

Bacterial shape: rod

Gram stain: Gram-

Distinguishing features that separate it from many other bacteria:

Member of family Enterobactereriacae

Ferments lactose, distinguishing it from the other highly related enterics bacteria Shigella, Salmonella and Proteus

Description of environment where it is most often found or has most effect and main relevance in environment:

Major inhabitants of the colon of humans and other warm blooded mammals

Causes diarrheal disease and urinary tract infections

Most common cause of Gram- sepsis

Pathogenic strains subdivided into seven categories (The first six cause diarrheal disease)

      Enterotoxigenic (ETEC)= produce toxins ST and LT to cause diarrhea

      Enteroinvasive (EIEC)= can invade and multiply within intestinal epithelial cells

      Enteropathogenic (EPEC)=

            form attaching and effacing (AE) lesions that destroy brush border microvilli

      Enterohemmorhagic (EHEC)=

            make AE lesions and produce Shiga-like toxins 1 and 2

            causes bloody diarrhea and cramping

            O157:H7 fall within this group

      Enteroaggregative (EaggEC)=

            see clumps of bacteria in Ňstacked brickÓ appearance

            unknown how it causes diarrhea

      Diffusely adhering (DAEC)=

            bacteria bind all over epithelial cells

            causes disease in malnourished or immunologically na•ve children

      Uropathogenic (UPEC)= most common cause of urinary tract infections

 

Describe two proteins that are important to its relevance:

LT toxin of ETEC binds to epithelial cells and activates adenylate cyclase to increase production of cAMP in the cell.  Causes a secretion of electrolytes and water into the small intestine, causing diarrhea.  Cholera toxin works by the same mechanism.  ST toxin works by a similar manner, increasing cGMP production in the cell.

 

Shiga-like toxins 1 and 2 of EHEC strains thought to kill vascular endothelial cells.  Appears to be the problem in hemolytic uremic syndrome that leads to kidney failure and thrombotic thrombocytopenic purpura causing strokes in the elderly.

 

Mode of transmission (pathogens):

Transmission to humans usually through contaminated food or water

Contaminated hamburger, unpasteurized fruit juice, salami, vegetables, and fruits have been source of outbreaks.

Infectious dose of 500 microorganisms can cause disease

Primary cause of nosocomial UTIs (urinary tract infection) due to catheters

 

Treatment or vaccine (pathogens):

Diarrheal disease primarily treated with rehydration and electrolytes.

Antibiotics used include doxycycline and trimethroprimsulfamethoxazole.

 

Biotechnological applications:

Model experimental organism used for understanding DNA replication, RNA transcription, protein translation

First recombinant protein made in E.coli (insulin)

 

Most interesting fact you learned about your bacterium:

Fluid flow was thought to be a major factor for flushing bacteria out of the bladder when infected.  Surprisingly, a recent in vitro study shows that bacteria actually bind more tightly (via fimbriae) when fluid velocity going past them increases!