Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 1 Chapter 21 Low G + C Gram-Positive Bacteria: The Firmicutes

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 2 Gram-Positive Bacteria Grouped based on shape (rods, cocci, or irregular) and ability to form endospores Bergey’s Manual of Systematic Bacteriology, 2 nd edition used phylogenetic relationships –Low G + C (Volume 3) –High G + C (Volume 4)

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 3 Figure 21.1

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4 Low G + C Gram-Positive Bacteria Bergey’s Manual placed in phylum Firmicutes –10 orders, 34 families –divided into 3 classes Mollicutes Clostridia Bacilli

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 5 Figure 21.2; phylogenetic relationships in the phylum firmicutes (Low G+C)

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 6 Class Mollicutes (The Mycoplasmas) contains five orders and six families lack cell walls and are pleomorphic –cannot synthesize peptidoglycan precursors –sterols may stabilize plasma membrane terminal structure aids in attachment to host cell –smallest bacteria capable of self-reproduction –grow as fried egg appearance on agar surface

7 Figure 21.3; the pleomorphic nature of Mycoplasma

8 Figure 21.4; colonies of Mycoplasma on agar

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10 More about Mycoplasma genomes –less than 1000 genes –one of the smallest found in prokaryotes

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 11 Metabolism of Mycoplasmas chemoorganotrophs –some produce ATP by glycolysis and lactic acid fermentation –some catabolize amino acids and urea –some have functional pentose phosphate pathway –none have complete TCA cycle –deficient in a number of biosynthetic pathways

12 Figure 21.5; energy conservation in Ureaplasma urealyticum 1.Once inside the cell (through the urea transpoter, ureas catalyzes the hydrolysis of urea to NH3 and CO2 2. Amonia accepts a proton to become NH4 which is exported to outside through the NH4 uniporters (AMT) 3.Once outside the cell, NH4 is converted to NH3 and H providing the proton to derive ATP synthesis

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 13 Gliding Motility most nonmotile; some have gliding motility –They move 2 to 5 microns/second –self surface proteins surround “neck” of cell attach to cytoskeletal proteins and function life microscopic legs powered by ATP hydrolysis

14 Figure 21.6; two forms of gliding motility in Mycoplasma Motor proteins that cause the cell to expand and contract Proteins that behave like legs that move the cell

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 15 Important Pathogens Mycoplasma mycoides – pleuropneumonia in cattle Mycoplasma gallisepticum – chronic respiratory disease in chickens Mycoplasma hyopneumoniae – swine pneumonia Mycoplasma pneumoniae – primary atypical pneumonia in humans Ureaplasma urealyticum – premature birth, neonatal meningitis and pneumonia spiroplasmas – pathogenic in insects, ticks, and a variety of plants

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 16 Class Clostridia 3 orders, 11 families largest genus is Clostridium –obligately anaerobic, fermentative, gram-positive, endospore forming

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18 Figure 21.7; Clostridium tetani endospores

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 19 Genus Clostridium over 100 species in distinct phylogenetic clusters fermentative metabolism (anerobic) –ferment amino acids using Stickland reaction oxidation of one amino acid using another as electron acceptor sodium motive force to drive amino acid uptake –fermentation products responsible for unpleasant odors associated with putrefaction

20 Figure 21.8; Stickland reactions Alanine is oxidized to acetate and glycine is used to oxidize the NADH which was generated during the alanine degradation

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 21 Figure 21.9

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 22 Genus Clostridium… great practical importance in following areas; –food spoilage through the Strickland reaction –industrial production of butanol –toxin production

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 23 Important Species of Clostridium C. botulinum –food spoilage (especially canned foods); botulism C. tetani – tetanus C. perfringens – gas gangrene C. acetobutylicum –manufacture of butanol

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 24 Genus Desulfotomaculum endospore forming reduces sulfate and sulfite to hydrogen sulfide during anaerobic respiration stains gram negative but in electron micrographs it is seen to have a gram- positive cell wall

25 Figure 21.10; Desulfotomaculum, with enodspores

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 26 Genera Heliobacterium and Heliophilum anaerobic, photosynthetic –bacteriochlorophyll g –have photosystem similar to green sulfur bacteria –Pigments located in plasma membrane –differ from anoxygenic photosynthetic bacteria in that they grow autotropically

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 27 Genus Veillonella gram negative but placed in order Clostridiales anaerobic, chemoheterotrophic –all have complex nutritional requirements normal biota of mouth, GI tract, urogenital tract of humans and animals found in infections of head, lung, and female genital tract

28 Class Bacilli large variety of gram-positive organisms contains two orders, Bacillales and Lactobacillales, 17 families and over 70 genera –includes cocci, rods, and nonspore forming rods

29

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 30 Genus Bacillus motile, peritrichous flagella, usually aerobic, catalase positive various species produce antibiotics Bacillus subtilis is type species –gram positive, facultative anaerobe –soil-dwelling, spore forming –may develop biofilms

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 31 Figure 21.12

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 32 Figure BiofilmFruiting body

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 33 Bacillus Subtilis used as model organism for –gene regulation, cell division, quorum sensing, cellular differentiation Whole genome was one of first to be sequenced – contains several families of genes which were expanded by gene duplication. e.g the genes encode the ABC transporters –18 genes code for sigma factors –  10 integrated prophages or remnants of prophages

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 34 Other Important Species of Bacillus B. cereus – food poisoning, Chinese fried rice B. anthracis – anthrax B. thuringiensis and B. sphaericus – used as insecticide –They synthesize the parasporal body – solid protein crystal that contains toxin

35 Figure 21.14;the parasporal body The prasporal body located beneath the spore Crystaline parasporal body

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 36 Genus Thermoactinomyces historically classified as actinomycete phylogenetic analysis –places it with low G + C microbes in order Bacillales, family Thermoactinomycetaceae true endospore former found in high temperature environments such as composts may be the cause of farmer’s lung disease

37 Figure 21.15; Themoactinomyces a. T. vulgaris areal mycelium b. Thin section of an endospore

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 38 Genus Sporosarcina only known endospore - former that has coccoid and not rod shape tolerates pH up to 10 –degrades urea to ammonia and carbon dioxide isolated from agricultural soils where animals urinate

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 39 Family Staphylococcaceae 5 genera, includes Staphylococcus facultatively anaerobic, nonmotile, gram-positive cocci usually form irregular clusters normally associated with warm-blooded animals in skin, skin glands, and mucous membranes

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 40 Figure 21.16; S. aureus

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 41 Staphylococcus Epidermidis common skin resident sometimes responsible for endocarditis and for infections of patients with lowered resistance –e.g., wound infections, surgical infections, and urinary tract infections

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 42 Staphylococcus Aureus most important human staphyloccoccal pathogen –e.g., abscesses, boils, wound infections, pneumonia, toxic shock syndrome –major cause of common food poisoning virulence factors –coagulase which causes blood plasma to clot –the toxin β-hemolysin lyses of Red Blood cells

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 43 S. aureus Antibiotic Resistance methicillin-resistant S. aureus (MRSA) and vancomycin resistant S. aureus (VRSA) –among most threatening antibiotic resistant VRSA may have no treatment –obtained from genetic elements received from other organisms –virulence factors also acquired from mobile genetic elements (transposons)

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 44 Genus Listeria short rods, facultative anaerobic, catalase positive motile by peritrichous flagella wide distribution in nature –common in decaying matter L. monocytogenes pathogen of humans and animals –Listeriosis - food-borne infection

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 45 Order Lactobacillales also called lactic acid bacteria (LAB) morphologically diverse –nonsporing –usually nonmotile ferment sugars for energy –lack cytochromes –fastidious contains several important genera

46 Order Lactobacillales largest genus - Lactobacillus –sometimes coccobacilli –grow optimally in slightly acidic conditions (pH 4.5 to 6.4) –Used to produce youghourt –two fermentation pathways homolactic fermentation (via glycolytic pathway) heterolactic fermentation (via pentose phosphate pathway)

47 Figure 21.17; heterolactic fermentation and the phosphoketolase pathway The phosphoketolase pathway converts glucose to lactate, ethanol and CO2

48 Figure 21.18; Leuconostoc mesenteroides

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 49 Genus Lactobacillus widely distributed in nature –on plant surfaces –in dairy products, meat, water, sewage, beer, fruits, and other materials –normal flora of mouth, intestinal tract, and vagina usually not pathogenic

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 50 Importance of Lactobacilli fermented products –vegetable products (sauerkraut, pickles, and silage) –beverages (beer, wine, juices, milk) sour dough bread Swiss cheese and other hard cheeses, yogurt sausages L. acidophilus – sold as probiotic agent Food spoilage – beer, wine, milk, meat

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 51 Family Leuconostocaceae Genus Leuconostoc facultative, gram-positive cocci heterolactic fermentation via –phosphoketolase pathway isolated from plants, silage, and milk

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 52 Importance of Leuconostoc wine production production of sauerkraut and pickles production of buttermilk, butter, and cheese synthesis of dextrans (L. mesenteroides) involved in food spoilage –tolerate high sugar concentrations and thus are problems in sugar refinaries –grow in heavy syrup

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 53 Families Streptococcaceae and Enterococcaceae chemoheterotrophic, mesophilic, nonspore forming cocci, usually nonmotile fermentative only aerotolerant and anaerobic groups –enterococci –lactococci –streptococci

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 54 Figure 21.19; Streptococcus S. payogenesS. agalactiae

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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 56 Genus Streptococcus hemolysis patterns used in Lancefield grouping; classification based on glycoproteins found on the cell surface. –alpha (  – hemolysis incomplete lysis of red blood cells seen as greenish zone around colony on blood agar –Beta (  hemolysis complete lysis of red blood cells seen as clear zone around colony on blood agar

57 Figure 21.20; Streptococcal hemolytic patterns S. aureus on blood agar Streptococcus on blood agar None hemolytic S. epidermidis

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 58 Three Groups of Streptococci pyogenic (pus producing) streptococci –e.g., S. pyogenes – streptococcal sore throat, acute glomerulonephritis, and rheumatic fever oral streptococci –e.g., S. mutans – dental caries other streptococci –e.g., S. pneumoniae – lobar pneumonia and otitis media

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 59 Important Enterococci and Lactococci Enterococcus faecalis –normal biotic in gastrointestinal tract –opportunistic pathogen (urinary tract infections and endocarditis) Lactococcus lactis – production of buttermilk and cheese