Bacteria An Overview. Bacteria Bacteria is the plural of bacterium Prokaryotic cells – no true...

BacteriaAn Overview

BacteriaBacteria is the plural of

bacteriumProkaryotic cells – no true

nucleusHave one double stranded

chromosomeMay have additional DNA called a

plasmidReproduce by binary fissionMost are benignSome are pathogenic

KingdomsTwo kingdoms include prokaryotic

cellsArchaebacteria

◦Extremophiles◦Methanogens - intestines◦Halophiles - salt◦Thermophiles – heat tolerance◦May have been on Earth for 3.5

billion years

Eubacteria – all other bacteria

ArcheabacteriaThermophile research in

Yellowstone has also proved benefical to the field of astrobiology.

Many scientists believe that thermophiles are most closely related to the primordial origin of life and can provide insight into early Earth as well as expand possiblities for life elsewhere in the universe

Archaebacteria

Filamentous BacterisYellowstone

Thermophile matsGrand Prismatic

Archaebacteria

Halophilic bacteria surviving in salt crystals.Owens Valley, California

Salt crust is colored red by dense colonies of halophilic archaebacteria. Sierra Nevada

Characterizing EubacteriaBacteria can be characterized by

shape

Characterizing BacteriaBacteria is also classified by their

oxygen requirementsAerobic Bacteria require oxygen

to support reproduction◦Esherichia coli

Anaerobic bacteria reproduce in the absence of oxygen◦Listeria◦Clostridium botulinum

Characterizing BacteriaFacultative bacteria reproduce

either in the presence or in the absence of oxygen.◦Salmonella◦Staphylococcus aureus◦Bacillus cereus

Characterizing BacteriaBacteria secrete a covering for

themselves - cell wallDo not contain cellulose like plant cell

wallsMostly made of peptidoglycan

(polypeptides bonded to modified sugars)

the amount & location of the peptidoglycan are different in the two possible types of cell walls, depending on the species of bacterium

Characterizing BacteriaSome antibiotics, like penicillin, inhibit the

formation of the chemical cross linkages needed to make peptidoglycan.

These antibiotics don’t outright kill the bacteria, but just stop them from being able to make more cell wall so they can grow.

That’s why antibiotics must typically be taken for ten days until the bacteria die (unable to grow)

If a person stops taking the antibiotic sooner, any living bacteria could start making peptidoglycan, grow, and reproduce.

Characterizing BacteriaDr. Hans Christian Gram, a

Danish physician, invented a staining process to tell the two types of bacteria apart, and in his honor, this process is called Gram stain.

Gram Stainthe amount of

peptidoglycan in the cell walls of the bacteria determine how those bacteria absorb the dyes with which they are stained

bacterial cells can be Gram+ or Gram -.

E.Coli and Staph

Gram StainGram+ bacteria have simpler cell

walls with lots of peptidoglycan, and stain a dark purple color.

Anthrax

Gram StainGram- bacteria have more

complex cell walls with less peptidoglycan, thus absorb less of the purple dye used and stain a pinkish color insteadE.coliPseudomonus aerugenosa

Gram StainGram- bacteria often incorporate

toxic chemicals (called endotoxin) into their cell walls, thus tend to cause worse reactions in our bodies.

antibiotics like penicillin are less effective against gram negative bacteria.

Ampicillin was developed to treat gram negative bacteria

Gram StainGram staining involves a four-

part process, which includes:◦crystal violet, the primary stain◦ iodine, the mordant◦a decolorizer made of acetone and

alcohol◦safranin, the counterstain