Chapter 3Resolution- Depends on the quality of lenses and wavelength of illuminating light- Maximum resolving power of most bright field microscopes is 0.2umDyes and Staining- Cells are frequently stained to observe organisms- Stains are made of organic salts- Dyes carry + or – charge on the molecule- Dyes divided in basic or acidic based on chargeo Basic dyes carry positive charge and bond to cell structures that carry a negative charge (cell wall) Commonly stain the cello Acidic dyes carry negative charges and are repelled by cell structures that carry a negative charge Commonly stain the background- Basic dyes are more commonly used than acidic dyes- Common basic dyes include:o Methylend blueo Crystal violeto Safranino Malachite green- Simple stain uses one basic stain to stain the cell- Differential stains are used to distinguish one bactieral group from anothero Two more common are: Gram stain Acid-fast stainGram Stain- Most widely used procedure for staining bacteria- Bacteria separated into two major groupso Gram-positive are stained blue or purpleo Gram-negative are stained red or pink- Involves four reagents1. Primary stain2. Mordanta. Makes an insoluble complex that holes the dye3. Decolorizera. 10-15 secondsb. Removes primary dye from gram negative cell4. Counter or Secondary staina. safraninAcid-Fast stain (AFB acid-fast bacilli)- Used to stain organisms that resist conventional staining- Used to strain members of genus Mycobacterium (Tuberculosis/Leprosy) and Nocardiao High lipid concentration (mycolic acids) in cell wall prevents uptake of dyeo Uses heat to facilitate stainingo Once stained, it is difficult to decolorize- Can be used for presumptive identification in diagnosis of clinical specimens- Requires multiple stepso Carbol fuchsin Colors acid-fast bacteria redo Decoloizer Generally acid alchohol Removes stains from non-acid-fast bacteriao Counter stain Methylene blue Colors non acid-fast bacteria blueMorphology of Prokaryotic Cells- Coccuso Spherical - Bacilluso Rod shaped- Vibrioo Curved rodo Vibrio cholera- Spirillumo Spiral shaped- Spirocheteo Helical- Pleomorphico Variable shapeo Mycoplasma- Pairs = diplococcic- Chains = streptococci- Strepto = short chaino Example: species of StreptococcusoBiofilms: develop an extracelluar matrix composed primarily of the tangled fibers of polysaccharides from the cells’ glycocalyses, plus DNA and proteinsPlanktonic  capsule/slime layer  adhere to surface65-70% of human bacterial infections involve biofilms100x more resistant to disinfectant and