Gram-positive bacteria

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Gram-positive bacteria
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Gram-positive bacteria Separated on basis of G
C content of chromosomal DNA Low G C
Gram-positives Firmicutes High G C
Gram-positives Actinobacteria
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Firmicutes (Low G C ) Divided into 3
classes Clostridia Mollicutes Bacilli F
urther divided into 10 orders and 34 families
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Class Mollicutes Composed of 5 orders and 6
families Commonly referred to as
mycoplasmas Are widespread and can be isolated
from animals and the environment Species can
cause diseases in humans, animals and plants e.g.
Mycoplasm pneumoniae
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Class Mollicutes Lack cell walls and are unable
to synthesize peptidoglycan Cells are
pleomorphic
(variably-shaped) Often require
sterols
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Class Clostridia
Divided into 3 orders and 10 families Largest
genus is Clostridium Anaerobes that form
endospores Genus contains over 100 species
(likely to be subdivided in the future)
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Class Clostridia
Many species can ferment amino acids using the
Stickland reaction C. botulinum - food
poisoning C. tetani - tetanus (lockjaw) C.
prefringens - gas gangrene
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Heliobacteria-Family Heliobacteriaceae Comprised
of genera Heliobacterium and Heliophilum Anaerob
ic gram-positive photosynthetic bacteria Stain
gram-negative due to lower than normal levels of
peptidoglycan
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Genus Veillonella Gram positive cocci with
complex nutritional requirements Parasites of
warm-blooded animals Some species are part of
the normal microbiota (mouth and vagina) Many
species are not thoroughly understood
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Class Bacilli Divided into 2 orders Bacillales
Lactobacillales Further divided into 17
families and over 70 species
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Order Bacillales
Genus Bacillus Largest genus in the
order Endospore-forming rods Many species
placed in new genera due to rRNA analyses
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Order Bacillales
Genus Bacillus B. subtilis is the type species
(chromosome has been sequenced) B. anthracis -
anthrax B. cereus - food poisoning B.
thuringiensis - insecticide
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Order Bacillales Genus Thermoactinomycetes Forma
lly grouped with the actinomycetes Thermophilic
(optimum temperature 45-60 ?C) Form aerial
mycelium like actinomycetes Commonly found in
hay stacks and compost heaps
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Order Bacillales
Genus Staphylococcus Facultative anaerobic
nonmotile cocci Associated with skin and mucous
membranes of animals
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Order Bacillales
Genus Staphylococcus S. epidermidis - human skin
normal microbiota S. aureus - abscesses,
pneumonia, toxic shock syndrome, food poisoning
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Order Lactobacillales Sometimes referred to as
lactic acid bacteria Major or some fermentation
product is lactic acid Nonspore-forming and
usually nonmotile
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Order Lactobacillales Genus Lactobacillus Can
carry out homolactic or heterolactic
fermentation Grow optimally under slightly
acidic conditions
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Order Lactobacillales Genus Lactobacillus (over
100 species) Many species used in the food and
dairy industry (e.g. L. bulgaris used in yogurt
production) Some species are responsible for
food spoilage
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Order Lactobacillales Genus Leuconostoc Facult
ative gram-positive cocci Many species used in
wine production, the fermentation of vegetables
and the production of dairy products Some
species are involved in food spoilage
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Order Lactobacillales Genus Streptococcus Large
complex genus Many species have been placed in
new genera (e.g. Enterococcus and
Lactococcus) Many species are the cause of
disease
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Order Lactobacillales Genus Streptococcus S.
pyogenes - strep throat, rheumatic fever S.
pneumoniae - pneumonia, ear infections S. mutans
- dental caries
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Order Lactobacillales
Genus Streptococcus Classified based on type
of hemolysis on blood agar plates Lancefield
grouping - grouping of ?-hemolytic streptococci
based on antigenic properties
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Actinobacteria (High G C gram-positive bacteria)
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Actinobacteria (High G C)
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Suborder Actinomycineae (Order Actinomycetales) I
rregularly-shaped aerobic or facultative
nonspore-forming rods Contain the genera
Actinomyces, Arcanobacterium, and Mobiluncus
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Suborder Actinomycineae
Genus Actinomyces Inhabit mucosal surfaces of
humans and other warm-blooded animals Often
found in the oral cavity Some species and cause
eye and gum infections (A. israelli)
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Suborder Corynebacterineae (Order Actinomycetales)
Contains 7 families with several well-known
genera Corynebacterium Mycobacterium Nocardia
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Suborder Corynebacterineae
Genus Corynebacterium Aerobic and facultative
curved rods Some species are saprophytes and
others are pathogens (e.g. C.
diphtheriae)
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Suborder Corynebacterineae
Genus Mycobacterium Aerobic rods that sometimes
branch or form filaments Grow very slowly Cell
walls have a high lipid content and contain waxes
(acid-fast)
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Suborder Corynebacterineae
Genus Mycobacterium Some species are human
pathogens M. tuberculosis - tuberculosis M.
leprae - leprosy
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Suborder Corynebacterineae
Genus Nocardia Found world-wide in soil and
aquatic environments Can form aerial mycelia
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Suborder Corynebacterineae
Genus Nocardia Can degrade hydrocarbons and
waxes Contribute to the deterioration of rubber
joints in sewer pipes
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Suborder Propionibacterineae (Order
Actinomycetales) Nonmotile nonspore-forming
anaerobic or aerotolerant rods Species of genus
Propionibacterium found on skin and digestive
tracts of animals Some species used in the
production of Swiss cheese P. acnes involved in
body odor and acne
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Suborder Streptomycineae (Order
Actinomycetales) Contains 1 family and 3
genera Most important genus is
Streptomyces About 500 species of Streptomyces
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Genus Streptomyces
Strict aerobes that produce aerial hyphae Found
in soil (1-20 of culturable population) Play
a major role in mineralization
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Genus Streptomyces
Produce many important antibiotics (e.g.
chloramphenicol, streptomycin, tetracycline) A
few are involved in causing diseases in plants
and animals
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Suborder Frankineae (Order Actinomycetales) Spore
-forming bacteria that form hyphae Many species
of the genus Frankia grow symbiotically in
association with plant roots
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Order Bifidobacteriales
Composed of 1 family and 10 genera Nonmotile
nonspore-forming rods Can be found in the mouth
and intestinal tracts of animals