EBIO 3400 1st Edition Lecture 16Outline of Last Lecture I. Genetics & Bacteria Outline of Current Lecture II. Gram positive bacteriaIII. Review of GC contentIV. FirmicutesV. The Nose and upper respiratory tractVI. The Lactic Acid BacteriaVII. Streptococcal DiseasesVIII. LactobacilliIX. Wine and lactic acid bacteria Current LectureI. Gram Positive Bacteria Gram-positive bacteria comprise two distinct phylogenetic branches:a. Phylum Firmicutesi. “Low-GC” species b. Phylum Actinobacteriai. “High-GC” speciesBoth groups have thick cell walls that retain the Gram stain—crystal violet.- Walls are reinforced by teichoic acidsII. Review of GC contentUsually expressed as a % GC content: (G+C / G+C+A+T) x 100G = GuanineC = CytosineA = AdenineT = ThymineDNA Helix: The top half of the molecule illustrates the typical double-helix structure that becomes magnified in the lower half to show individual bases and the hydrogen bonding that holds the two strands together- Firmicutes = low GC, Gram positive bacteriaBacillusClostridiumThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.StaphylococcusLactobacillusStreptococcusIII. FirmicutesBacillales: Genus Bacillusa. Large rod-shaped cellsi. B. anthracisii. B. thuringiensisiii. B. subtilisb. Vegetative cells develop endospores in times of starvation and stress – secondary metabolismClostridiales: Genus Clostridiumc. Endospores, often a “drumstick.”d. C. botulinum; C. tetani; C. difficileBotox is used to relax muscle spasms Clostridiales: Metabacterium polyspora- Large (15–20 mm); grows in GI tract of guinea pigs- Forms multiple endospores- Cells undergo limited binary fission Clostridiales: Epulopiscium fishelsoni- HUGE (can be seen with the naked eye)- Grows in GI tract of surgeonfish- Gives “live birth” to two internal offspring - Cells do not undergo binary fissionNON-spore forming firmicutes: Both Bacillales and Clostridiales, as well as other Gram-positive orders, include many non-spore-forming rods and cocci But many others as well e.g.  Lactic acid bacteria Listeria Staphylococcus Mollicutes (= Mycoplasmas = Tenericutes)  Listeria monocytogenes Facultative anaerobic rod Contaminates cheese, sauerkraut, vegetables, meats – is a pschrotroph Causes Listeriosis A severe gastroenteritis that can progress to the nervous system Hides in macrophages Staphylococcus: Facultative anaerobes, Cocci in clusters, S. aureus, MRSA facultatively anaerobic, nonmotile, cocci that form irregular clusters – most closely related to Bacillus Cells divide in multiple planes thus they from irregular groups as opposed to streptococciwhich divide in one plane thus forming strips. No endosporesIV. The Nose and upper respiratory tractStaphylococcus aureus and S. epidermidis are the predominant bacteria in the nose.20% (much higher % among hospital workers) of humans carry S. aureus, an opportunistic pathogenDiseases caused by S. aureus: toxic shock syndrome, food poisoning, boils (furuncles), pimples and many more Mollicutes (= Mycoplasmas = Tenericutes)  Mollicutes Latin = “soft skin” / Firmicutes Latin = “hard skin”- Completely lost their cell walls and S-layers - Best known genus is Mycoplasma- Causes pneumonia and meningitis DISCUSS LATER IN COURSE- Pleomorphic cells- “Fried egg”–shaped coloniesV. The Lactic Acid BacteriaMembers of the low GC Gram + Firmicutes **DO NOT form endospores Lactic acid bacteria are fermentative bacteria that can tolerate O2 but can't use O2 in their metabolism (aerotolerant). Mostly fermentative Live in rich environments (like your throat or milk) and have lost the ability (through evolutionary time) to synthesize many amino acids and vitamins. Such organisms are referred to as fastidious• Produce lactic acid as fermentation product Homolactic fermentation = homofermentative only lactic acid (2 per sugar fermented) Heterolactic fermentation = heterofermentative other things, too (usually 1 lacticacid and 1 acetaldehyde or alcohol) Heterolactic fermentation - don’t memorize pathway just note products are ;lactic acid, ethanol and gas (CO2) Streptococci = genus Streptococcus (strept = Gr. for twisted): • some are important pathogens (e.g. S. pneumoniae and S. mutans) • very common inhabitants of the human body and foods (will come back to…).  Homolactic fermentation (produce 2 lactic acid for every glucose used in fermentation)VI. Streptococcal Diseases• Various Streptococcus speciesDental caries: tooth demineralization due to lactic acid production in plaque S. mutans and other streptococci are a major cause of dental caries via an plasmid-encoded enzyme dextransucrase which catalyzes the following:n sucrose ----> dextran + n fructose  Dextran is a sticky polymer (alpha-1,6 linkages) of glucose molecules (we don’t have the enzyme to cleave that bond). S. mutans is also homofermentative so it also converts every fructose from above to 2 lactic acidsn sucrose ----> n dextran + 2n lactic acid Caries are caused by this acid eating away at the enamel Dental plaque: Biofilm bacterial community on teeth Many types of Bacteria in a polysaccharide matrix Increase in acidity after sugar addition to dental plaque Sugar and S. mutans are needed because S. mutans can’t cause caries without sugar and S. mutans-free animals don’t get cavities even in the presence of sucroseVII. Lactobacilli* Low GC • Lactobacillus (and Lactococcus = streptococci found in food) used to make many foods - yogurt, sauerkraut, beer, wine, cheese, sour dough bread Around 109 Lactobacillus cells per gram of yogurt-Usually rods, can live at lower pHs than Streptococcus spp. thus is important in later stages of food fermentations (e.g. in yogurt, sauerkraut). Homo- or heterolactic fermenters Lactobacillus cells attached to vaginal epithelial cells. About 30% of women have high levels of L. acidophilusA. Ecology of yogurt makingStreptococcus thermophilus vs. Lactobacillus delbruekii subsp. bulgaricus vs. assorted pathogens.1. Scald milk (= heat to simmering and then cool to 48°C). This step kills most of the organisms in the milk.2. Inoculate with yogurt3. Incubate at 48°C (= temp. optimum for S. thermophilus). This allows S. thermophilus to grow and produce lactic acid.4.