Overview of Gram-Positive and Other Bacteria Bacteria has many phyla other than Proteobacteria,...

Overview of Gram-Positive and Other Bacteria

• Bacteria has many phyla other than Proteobacteria, including

– Gram-positive bacteria• Large group of mostly chemoorganotrophs

– Cyanobacteria• Oxygenic phototrophs that have evolutionary

roots near those of gram-positive bacteria

– Phylogenetically early-branching phyla• Such as Aquifex

– Other morphologically distinct groups© 2012 Pearson Education, Inc.

I. Firmicutes, Mollicutes, and Actinobacteria

• Gram-positive bacteria are a large and diverse group

• Divided into three groups:– Firmicutes

– Mollicutes

– Actinobacteria

© 2012 Pearson Education, Inc.

18.1 Nonsporulating Firmicutes

• Key genera: Staphylococcus, Streptococcus, Lactobacillus, Sarcina

• Staphylococcus and Micrococcus (Figure 18.1)– Aerobic, cocci

– Resistant to reduced water potential

– Tolerate high salt

– Many species are pigmented

– Staphylococcus aureus


Figure 18.1


18.1 Nonsporulating Firmicutes

• Streptococcus – Play important roles in production of buttermilk,

silage, and other products

– Some species are pathogenic

– Lactococcus: genera of dairy significance (Figure 18.3)

– Enterococcus: genera of fecal origin


Figure 18.3


18.2 Endospore-Forming Firmicutes

• Key genera: Bacillus & Clostridium– Distinguished on the basis of cell morphology,

and the shape and cellular position of endospore

– Generally found in soils

– Endospores are advantageous for soil microorganisms


Figure 18.5



• Bacillus– Many produce extracellular hydrolytic enzymes

that break down polymers

– Many bacilli produce antibiotics

– Bacillus thuringiensis produces insect larvicides (Figure 18.6)


Figure 18.6

EndosporeCrystal



• Clostridium– Lack a respiratory chain, anaerobic

– Mainly found in anaerobic pockets in the soil• Also live in mammalian intestinal tract

– Some cause diseases such as botulism, tetanus, and gangrene


18.3 Mollicutes: The Mycoplasmas

• Key genera: Mycoplasma– Lack cell walls

– Some of the smallest organisms capable of autonomous growth

– Parasites that inhabit animal and plant hosts

– Key components of peptidoglycan are missing

• Mycoplasma cells are pleomorphic– Cells may be cocci or filaments of various lengths


Figure 18.9


18.4 Actinobacteria: Coryneform & Mycobacteria

• Key genera: Corynebacterium & Mycobacterium

– Actinobacteria form their own phylum– Over 30 taxonomic families– Rod-shaped to filamentous, usually aerobic– Mostly harmless commensals

(Mycobacterium are exceptions)– Valuable for antibiotics and certain fermented

dairy products


18.4 Actinobacteria: Coryneform & Propionic Acid Bacteria

• Corynebacterium– Gram-positive, aerobic, nonmotile, rod-shaped

– Form club-shaped, irregular-shaped, or V-shaped cell arrangements

– Extremely diverse


Figure 18.12


18.5 Actinobacteria: Mycobacterium

• Mycobacterium– Rod-shaped organisms, exhibit acid-fastness

(Figure 18.15)

– First discovered by Robert Koch

– Not readily stained by Gram stain because of high surface lipid content


Figure 18.16


18.6 Filamentous Actinobacteria: Streptomyces & Relatives

• Key genera: Streptomyces, Actinomyces (Figure 18.18)

– Filamentous, gram-positive bacteria– Produce mycelium analogous to mycelium of

fungi– Over 500 species of Streptomyces– Streptomyces spores are called conidia

(Figure 18.19)– Primarily soil microorganisms, responsible for

earthy odor of soil (geosmins)– Strict aerobes that produce many extracellular

enzymes


Figure 18.18


18.6 Filamentous Actinobacteria: Streptomyces & Relatives

• Streptomyces (Figure 18.22)– 50% of all isolated Streptomyces produce

antibiotics (Figure 18.23)

– Over 500 distinct antibiotics produced by Streptomyces

– Some produce more than one antibiotic

– Genomes are typically quite large (8 Mbp and larger)

– Knowledge of the ecology of Streptomyces remains poor


Figure 18.22


Figure 18.23


18.7 Cyanobacteria

• Phototrophic• Gas vesicles are found in many cyanobacteria

– Help maintain buoyancy

– Keep cell in water column where there is light

• Heterocysts are rounded, enlarged cells– Anoxic environment inside heterocyst

– Site for nitrogen fixation

– Nitrogenase is sensitive to oxygen


Figure 18.24


Figure 18.26 Heterocyst

Glutamine

Heterocyst

Vegetative cells Vegetative cells


18.9 The Chlamydia

• Key genera: Chlamydia• Obligately parasitic with poor metabolic

capacities– Some of the simplest biochemical capacities

of all known bacteria

• Currently one of the leading sexually transmitted diseases


Figure 18.30


Figure 18.31

Elementary bodies

Elementary body

Reticulate body

Release ofelementary bodies

Conversion toelementary bodies

Phagocytosis ofelementary body

Elementary bodyattacks host cell

Multiplicationof reticulatebodies

Conversion toreticulate body


18.10 Planctomyces: A Phylogenetically Unique Bacterium

• Key genera: Planctomyces

• Planctomyces is a budding bacterium – Facultative aerobic chemoorganotroph

– Stalked

– Primarily aquatic

– Extensive cell compartmentalization including a membrane-enclosed nuclear structure


Figure 18.32

Flagellum

Stalk

Pilus

Stalk


Figure 18.33

Nucleoid

Nuclearenvelope


Bacteroides

• Key genera:• Bacteroides

– Obligately anaerobic– Numerically dominant bacterium in human

intestinal tract


18.15 Chlorobium and Other Green Sulfur Bacteria

• Key genera: Chlorobium– Phylogenetically distinct, nonmotile, anoxygenic

phototrophs– Utilize H2S as an electron donor and oxidize it

to SO42

– Have chlorosomes bacteriochlorophyll-rich bodies bounded by a thin membrane

– Green- and brown-colored species exist


Figure 18.39


18.15 Chlorobium and Other Green Sulfur Bacteria

• Green sulfur bacteria inhabit anoxic environments rich in H2S

• Some green sulfur bacteria form consortia– Involves the green sulfur bacterium and a

chemoorganotrophic bacterium


18.16 Spirochetes

• Key genera: Spirochaeta, Treponema, Leptospira, Borrelia

– Gram-negative, motile, and coiled

– Widespread in aquatic environments and in animals

– Have endoflagella: located in the periplasm of the cell

– Also found in the rumen of animals


Figure 18.42


Figure 18.43

Endoflagellum

Protoplasmiccylinder

Outersheath

Endoflagellum (rigid,rotates, attached to oneend of protoplasmiccylinder)

Outer sheath(flexible)

Protoplasmic cylinder(rigid, generally helical)


18.16 Spirochetes• Spirochaeta

– Free-living, anaerobic and facultatively anaerobic spirochetes

• Treponema (Figure 18.45a)– Anaerobic host-associated spirochetes that

are commensal or parasites of humans

• Borrelia (Figure 18.45b)– Majority are human or animal pathogens

– Borrelia burgdorferi is the causative agent of Lyme disease

• B. burgdorferi has a linear chromosome


Deinococcus

• Deinococcus– Gram-positive, aerobic, organotrophic

– Most are red or pink due to carotenoids

– Resist UV radiation, gamma radiation, and desiccation

– Resistant to most mutagenic agents


18.20 Aquifex

• Key genera: Aquifex– Aquifex

• Obligately chemolithotrophic hyperthermophile• Most thermophilic of all Bacteria (can grow at 95C)• 1.55-Mbp genome


Overview of Gram-Positive and Other Bacteria Bacteria has many phyla other than Proteobacteria,...

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