• Gram negative
• Gram positive
• No cell wall

1. Cocci
2. Lactic Acid Bacteria
3. Rods
4. Other groups

1. Cocci (general)

• Contain outer membrane
• Unique phylogenetically
• Red pigments: carotenoids.
• Very resistant to mutagenic chemicals - radiation
• Powerful DNA repair system

• Pairs, chains or clusters.
• Resistant to low H₂O activity
• Tolerate drying and high salt (mannitol salt agar)
• Catalase positive

• Saprophytic obligate aerobes
• Isolated from skin, nasal passage, soil or freshwater
• Food spoilage: cured meats, maple syrup

• Facultative anaerobes with cells in clusters
• Common parasite and opportunistic pathogen of humans and animals
• Habitat: skin and mucous membranes

• S.epidermidis: non-pigmented and coagulase negative occasionally causes hospital acquired infections

• S.aureus: yellow pigmented and coagulase positive

• Virulence factors of S.aureus: coagulase and toxins (hemolytic, systemic shock, exfoliating, leukolytic, cytolytic)

• Obligate anaerobes
• Produce organic acids, volatile fatty acids, and gases as fermentation endproducts
• Require complex nutrients e.g. vitamins
• Inhabitants of humans and animals

• 5 Genera: Peptococcus, Peptostreptococcus, Ruminococcus, Coprococcus and Sarcina

1. Lactic Acid Bacteria

• Non-motile, non-sporulating, aerotolerant rods or cocci

• Lactic acid as major or sole product of fermentation

• Generally require complex nutrients
• Low G+C% group

• substrate level phosphorylation (two pathways):

Streptococcus

• homofermentative
• Cells in pairs or chains

• Habitats: Mouth, mucous membranes, gastrointestinal tract, upper respiratory tract

• Opportunistic pathogens producing haemolysins (a - or b -haemolysis)

• Divided into Lancefield Antigenic groups (A-H, J-U)

• S.pyogenes (Lancefield A): many diseases including streptococcal pharyngitis and scarlet fever

• Virulence factors of S.pyogenes: M protein on cell surface and exotoxins

• S agalactiae (Lancefield B): numerous diseases including venereal disease

• S.pneumoniae major cause of bacterial pneumonia and meningitis

• S.mutans: tooth decay

• S.mitis: infective endocarditis
• S.lactis and S.cremoris: important in dairy industry

• Homofermentative opportunistic pathogen

• Habitat: gastrointestinal tract

• Indicator organism

• E.faecalis: infective endocarditis

• Morphologically similar to Streptococcus
• Heterofermentative
• Important in the food industry

• Regular shaped, non-spore forming, saprophytic, facultative anaerobic rods
• Homofermentative and heterofermentative metabolism
• Habitats: fermenting animal or vegetable products, or parasites of the mouth, vagina and intestinal tract

• Three major subgroups and 70 different species

• Protect against infection from pathogens
• L.acidophilus: probiotic

• Important in the food industry eg. fermented dairy products

Other Lactic acid bacteria

• Homofermentative metabolism
• Used in the food industry
• Lactococcus, Pediococcocus and Pediococcus

1. Rods

• Endospores: resistant to drying, radiation, disinfectants and heat
• Means of survival not replication or growth.
• Can remain dormant for long periods of time

• Either aerobic or anaerobic

• Very heterogenous group of bacteria
• Obligate aerobic or facultative anaerobic
• easily isolated from soil and many other environments
• Heterotrophic and use a wide range of carbon
• Some produce antibiotics and extracellular hydrolytic enzymes
• Can be acidophiles, alkalophiles, mesophiles, thermophiles, psychrophiles

• Characteristic diaminopimelic acid in cell wall

• Some pathogenic others important industrially

• spherical terminal endospores
• Contains lysine or ornithine in cell wall
• Use organic acids or amino acids for carbon
• Alkalophilic

• Facultative anaerobes
• Oval star-shaped endospores
• Produce antibiotics (polymyxins)
• Produce 2,3 butanediol

• Wide temperature range for growth

• Produce antibiotics (bacitracin)

• Produce antibiotics (gramicidin and tyrocidin)

• Grow optimally above 50ºC, up to 75ºC
• Flat sour spoilage of canned foods
• Commercial uses: molecular biology and heat sterility

• Commercial uses: proteases

• Produce antibiotics (bacitracin)

• Commercial uses: a -amylases

• Oval central endospores
• Human pathogen
• Food poisoning: rice, raw milk and meat products

• Facultative anaerobe
• Animal and human pathogen
• Disease: anthrax (cutaneous or pulmonary)
• Agent for biological warfare

• Entomopathogens (insect)
• Milky disease: Japanese beetle
• Causes septicemia

• Entomopathogens (insect)

• Disease: intoxication of insects (lepidopterans, dipterans, coleopterans)
• Produces parasporal protein crystal (Bt toxin)
• Protoxin ® toxin: epithelial cell pore formation
• Genetic engineering uses

• Obligate anaerobes
• Thermophilic, acidophilic or mesophilic
• Produce oval or spherical terminal, subterminal or central spores
• Habitat: almost every anaerobic environment
• ATP from substrate-level phosphorylation during fermentation
• Utilize a wide variety of substrates and produce numerous fermentation end-products
• Metabolically classified according to fermentation of sugars (saccharolytic) or proteins (proteolytic)

• Some pathogenic others important industrially

• Spoilage and gas production in milk (C.butyricum)
• Spoilage of canned food (Thermophilic species eg C.thermosaccharolyticum)
• Industrial production of acetone and butanol (C.acetobutylicum)

• Large spherical terminal endospores
• Habitat: intestines of herbivorous animals and soil
• Disease: tetanus (deep wounds)
• Highly potent exotoxin (neurotoxin) causing lockjaw and paralysis

• Oval terminal endospores
• Habitat: soils, lake and marine sediments
• Disease: botulism (food poisoning, infant and wound)

• Highly potent exotoxin (neurotoxin) causing flaccid paralysis

• Oxygen tolerant
• Subterminal spherical endospores
• Habitat: large intestine of humans and animals
• Diseases: gas gangrene and gastroenteritis (food poisoning)

• Toxins: hemolytic, collogenase, protease, enterotoxins

• Endospore-forming aerobic cocci
• S.halophila: marine habitat and requires sodium ions
• S.ureae: soil habitat and breaks down of urea.

• Anaerobic respiration by sulfate reduction

• Uniform appearance
• Chemoorganotrophic
• Require complex nutrients
• Habitats: soil, water, food products, humans and animals

• Members: Listeria, Lactobacillus, Brocothrix, Carnobacterium, Kurthia and Erysipelothrix

• Short motile rods, facultative anaerobe
• Growth enhanced in the presence of glucose, serum and blood

• L.monocytogenes: listeriosis (food poisoning)

• Animal parasite
• E.rhusiopathiae: swine erysipelas and erysipeloid

• Pleomorphic and irregular shaped
• Mainly saprophytic but some pathogenic
• Primarily inhabit soils but some found on skin, plants, milk and cheese
• Aerobic: Arthrobacter, Brevibacterium, Aeromicrobium, Clavibacter and Terrabacterium
• Facultative anaerobic: Corynebacterium, Cellulomonas and Propionobacterium

• Saprophytes, plant, animal and human pathogens
• Displays snapping division
• C.diphtheriae: diphtheria
• C.glutamicum: industrial production of organic acids as food supplements (eg MSG)

• Aerotolerant pleomorphic rods
• Ferment lactic acid, carbohydrates, alcohols with propionic acid as an end product
• Habitat: animals (rumen) and human skin
• Important in food industry (cheese manufacture)

• P.acnes: cutaneous infection leading to acne

1. Special groups

• Large group of phylogenetically distinct bacteria

• Mycelium: network of branching filaments (hyphae)

• Most form spores (conidiospores or sporangiospores) in mycelia

• Habitat: soils, water, decayed vegetation and wastewater

• Differentiation is based mainly on the mycelium, conidia and sporangia
• Important in antibiotic production

• Soil bacteria that produce conidiospores and form aerial mycelia
• Exoenzymes that degrade polysaccharides, proteins, fats
• Produce antibiotics

• Multiply by fragmentation of the hyphae
• Some contain mycolic acid in cell wall (acid-fast)
• Degrade petroleum compounds
• Can produce antibiotics

• Branching filaments
• Nitrogen fixing

• Obligate aerobic thin pleomorphic bacteria
• Either saprophytic or human and animal pathogens
• Habitat: soils and water
• Contain waxy mycolic acids in cell wall
• Acid-fast cell wall
• Resistant to desiccation, most antibiotics, phagocytosis
• Utilise a wide variety of carbon compounds, sugars, fats, hydrocarbons, aromatics.
• Growth rate: fast or slow
• M.tuberculosis: tuberculosis
• M.bovis: tuberculosis
• M.leprae: leprosy

• No rigid cell wall. pleomorphic and stain gram negative
• Phylogenetically placed within gram positive
• Resistant to antibiotics that affect cell wall
• Require complex nutrients, most need cholesterol for growth
• Habitat: mucous membranes of animals and humans and vascular tissues of plants
• Growth by regular binary fission or cellular elongation

• Parasites in mucous membranes of animals
• M.pneumonia: pneumonia

Toxicity: end products (ammonia, peroxides)

• M.hominis: pelvic inflammatory disease

• Helical motile cells
• Disease in citrus plants