7.10
Bacterial Phylum Spirochaetes
Spirochetes, unique bacteria in the phylum Spirochaetes, are gram-negative, motile, tightly coiled, slender, and flexible. They inhabit aquatic sedime…
Spirochetes are Gram-negative, coiled bacteria classified in the phylum Spirochaetes.
Endoflagella in spirochetes produce corkscrew-like motion, enabling movement through viscous materials or tissues.
The Spirochaeta genus includes anaerobic and facultatively aerobic spirochetes that are free-living in freshwater, sediment, and oceans.
Notable species include Spirochaeta plicatilis from sulfidic freshwater and marine environments.
Cristispira is a genus of spirochetes that are found in the crystalline style of many bivalve mollusks like clams, mussels, and oysters.
The genus Treponema includes anaerobic or microaerophilic spirochetes that are commensals or pathogens of humans and animals, such as Treponema denticola, common in the human oral cavity.
Many species in the genus Borrelia are pathogenic. Borrelia burgdorferi, for example, causes Lyme disease, which is transmitted by ticks.
The genera Leptospira and Leptonema are strictly aerobic spirochetes that oxidize long-chain fatty acids, like oleic acid, from their host's tissues or the environment to support their growth. Leptospira interrogans is parasitic in humans and causes leptospirosis.
View the full transcript and gain access to JoVE Core videos
Q1: What are endoflagella and how do they enable spirochete movement?
Endoflagella are flagella located within the periplasm, anchored at cell poles and extending along the cell length. When they rotate, they create torsion that causes the cell to flex and move in a corkscrew-like motion. This unique motility allows spirochetes to penetrate viscous materials and tissues effectively.
Q2: How do spirochetes differ from spirilla bacteria?
Spirochetes and spirilla are both coiled bacteria, but spirilla are helical, rod-shaped cells with polar flagella that lack the outer sheath and endoflagella found in spirochetes. Spirilla are more rigid and larger, while spirochetes are thin, around 0.5 micrometers, and highly flexible, enabling their distinctive corkscrew motility.
Q3: What habitats do free-living spirochetes in the genus Spirochaeta occupy?
Spirochaeta species are anaerobic and facultatively aerobic bacteria found in freshwater, sediments, and oceans. Spirochaeta plicatilis inhabits sulfidic freshwater and marine environments, while Spirochaeta stenostrepta is an obligate anaerobe in hydrogen sulfide-rich muds where it ferments sugars into ethanol, acetate, and lactate.
Q4: Which spirochete genera include human pathogens and what diseases do they cause?
Treponema pallidum causes syphilis and is unusually thin at 0.2 micrometers with a flat, wavy morphology. Borrelia burgdorferi causes Lyme disease, transmitted by ticks. Leptospira interrogans causes leptospirosis, leading to kidney and liver damage, nephritis, jaundice, and potentially renal failure in humans.
Q5: What is the unique ecological role of Cristispira spirochetes?
Cristispira is a genus of spirochetes found exclusively in the crystalline style of bivalve mollusks like clams, mussels, and oysters. These bacteria aid in food processing within the mollusk digestive tract. Cristispira has not been cultured, and its specific adaptation to this specialized habitat remains unclear.
Q6: How do Leptospira and Leptonema spirochetes obtain energy for growth?
Leptospira and Leptonema are strictly aerobic spirochetes that oxidize long-chain fatty acids, such as oleic acid, from their host tissues or the environment to support their growth. Leptospira species are thin, finely coiled, and typically bent into a hook at each end, with both free-living and parasitic forms.
Q7: How are spirochetes classified within microbial diversity?
Spirochetes are gram-negative, coiled bacteria classified in the phylum Spirochaetes and divided into eight genera based on habitat, pathogenicity, phylogeny, and characteristics. Understanding their classification through methods of classification and identification helps distinguish them from other bacterial phyla and reveals their ecological and medical significance.