PART 1 Prokaryotic Microbes

Contains 23 phyla, 32 classes, 5 subclasses, 77 orders, 14 suborders, 182 families, 871 genera, and 5,007 species.

Phenotypic categories• Gram-negative and have cell wall• Gram-positive and have cell wall• Lack cell wall.

Cell morphology Staining reactions Motility Colony morphology Atmospheric requirements Nutritional requirements Biochemical and metabolic activities Specific enzymes that the organism produces Pathogenecity Genetic composition

Shapes and Arrangements of Bacteria(Separate Presentation)

Bacteria can lose their characteristic shape because of adverse growth condition which prevents the production of normal cell wall.

Some can revert back to normal shape while others cannot.

Mycoplasma do not have cell walls. Pleomorphism- ability to exist in variety of

shapes.

Mycoplasma pneumoniae

Preparation of smear Heat fixation Methanol fixation Purpose of fixation:

• Kills the organism• Preserves their morphology• Anchors the smear to the slide

Simple staining• Determine the morphology• Dye is applied to the fixed smear, rinse, dried and

examined using OIO. Structural staining

• Use to observe bacterial capsules, spores, and flagella.

Differential staining• Gram staining• Acid-fast staining

Gram-positive & Gram-negativeGram-positive & Gram-negative

Gram Positive Gram Negative

Color Blue-to-purple Pink-to-red

Peptidoglycan Thick layer Thin layer

Teichoic acids and lipoteichoic acids in cell walls

Present Absent

Lipopolysaccharide in cell walls

Absent Present

Difference between Gram-positive and Gram-negative Bacteria

Clostridium tetani Bacillus subtilis

Gram-positive bacteria tend to be killed by penicillin and detergents.Gram-negative bacteria are more resistant to antibiotics.

Use to identify Mycobacteria spp. Carbol fuschin (bright red) is driven into

the bacterial cell using heat. Heat softens the waxes of the cell walls of

Mycobacteria, enabling the stain to penetrate.

A decolorizing agent (acid-alcohol) is then used in an attempt to remove the red color from the cells.

Because Mycobacteria are not decolorized by the acid-alcohol, they are said to be acid-fast.

Most bacteria are non acid-fast. Acid-fast stain is especially used in TB

labs. Developed in 1882 by Paul Ehlrich.

Acid-fast staining: Mycobacterium leprae

Negative staining is useful for capsules. Endospores staining- heat is required to

drive a stain into endospores. Flagella staining requires a mordant to

make the flagella wide enough to see.

Motile and nonmotile Presence of flagella, axial filaments or

capable of gliding motility.

Endoflagella In spirochetes Anchored at one

end of a cell Rotation causes

cell to move

Bacterial colony- mound or pile of bacteria in a solid culture medium.

Contains million of organisms. Colony morphology varies from one

species to another.• Size• Color• Over-all shape• Elevation• Margin

Oxygen (O2)

Obligate aerobes

Facultative anaerobes

Obligate anaerobes

Aerotolerant anaerobes Microaerophiles

CO2- Canophiles

Nitrogen• In amino acids, proteins• Most bacteria decompose proteins• Some bacteria use NH4

+ or NO3

• A few bacteria use N2 in nitrogen fixation Sulfur

• In amino acids, thiamine, biotin• Most bacteria decompose proteins• Some bacteria use SO4

2 or H2S Phosphorus

• In DNA, RNA, ATP, and membranes• PO4

3 is a source of phosphorus

Organic Growth Factors• Organic compounds obtained from the

environment• Vitamins, amino acids, purines, pyrimidines

Carbon• Structural organic molecules, energy source

• Chemoheterotrophs use organic carbon sources

• Autotrophs use CO2

Trace Elements• Inorganic elements required in small amounts

• Usually as enzyme cofactors

Capsules Pili Endotoxins Exotoxins Exoenzymes

Nuclear area (nucleoid)

Figure 4.6a, b

Obligate intracellular parasites:• Ehrlichia and Anaplasma spp. Tick-borne,

ehrlichiosis• Rickettsia. Arthropod-borne, spotted fevers

R. prowazekii Epidemic typhus R. typhi Endemic murine typhus R. rickettsii Rocky Mountain Spotted Fever

Human pathogens:• Bartonella Trench fever• B. hensela Cat-scratch disease• Coxiella Q fever transmitted via aerosols

or milk

Chlamydia Energy parasites Mode of transmission:

inhalation of aerosols or direct contact between hosts

C. trachomatis• Trachoma• STD, urethritis

C. pneumoniae C. psittaci

• Causes psittacosis

Mycoplasma Wall-less, pleomorphic 0.1 - 0.24 µm M. pneumoniae Pleuropneumonia-like

organsims (PPLO) Tiny colonies (fried egg

colonies) Resistant to antibiotics

Thiomargarita namibiensis- largest bacteria (750 µm)

Epulopiscium fishelsonii- another enormous bacteria (80 µm X 600 µm)

Nanobacteria- less than 1 µm, found in soil, minerals, ocean water, dental plaque, and even rocks (meteorites)

Thiomargarita namibiensis

Epulopiscium fishelsonii

Nanobacteria

Includes purple bacteria, green bacteria and cyanobacteria.

Oxygenic photosynthesis Anoxygenic photosynthesis

2H2O + CO2

light(CH2O) + H2O + O2

2H2S + CO2

light(CH2O) + H2O + 2S0

Cyanobacteria

purple sulfur bacteria green sulfur bacteria

Discovered in 1977 Genetic contains 2 phyla, 8 classes, 12

orders, 21 families, 69 genera, and 217 species.

Genetically, archaeans are closely related to eukaryotes than bacteria.

ThermophilesThermophiles

Heat-loving archaebacteria found near hydrothermal vents and hot springs

Many thermophiles are chemosynthetic using dissolved sulfur or other elements as their energy source and iron as a means of respiration

HalophilesHalophiles

Thrive in unusually salty habitats. Some can thrive in water that’s 9% salt; sea water contains only 0.9% salt.

Have light-sensitive pigment bacteriorhopsodin which absorbs energy from sunlight

Example: Salt Lake and Dead Sea

PsychrophilesPsychrophiles

like extremely cold temperatures (even down to -10 degrees Celsius).

Live in arctic and antartic oceans

MethanogensMethanogens

are anaerobic archaebacteria that produce methane

are found in sewage treatment plants, bogs, and the intestinal tracts of ruminants.

ancient methanogens are the source of natural gas.

Next topic: Part 2 Eukaryotic Microbes