Large Symbiotic Spirochetes: Clevelandina, Cristispira, Diplocalyx, Hollandina and Pillotina
The genera Cristispira, Clevelandina, Diplocalyx, Hollandina, and Pillotina are morphologically complex, Gram-negative, motile, spirochetes (helical bacteria) in which the flagella are always entirely periplasmic (i.e., located between the inner “plasma”
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Large Symbiotic Spirochetes: Clevelandina, Cristispira, Diplocalyx, Hollandina and Pillotina LYNN MARGULIS AND GREGORY HINKLE
The genera Cristispira, Clevelandina, Diplocalyx, Hollandina, and Pillotina are morphologically complex, Gram-negative, motile, spirochetes (helical bacteria) in which the flagella are always entirely periplasmic (i.e., located between the inner “plasma” and the outer membrane typical of Gram-negative bacteria) (Fig. 1). (For a general discussion of the morphology of spirochetes, see Free-Living Saccharolytic Spirochetes: The Genus Spirochaeta in this Volume). All are obligate symbionts in the digestive system of mollusks or arthropods. These morphologically complex spirochetes have greater than 10 and sometimes as many as 300 flagella inserted at both ends of the cell and overlapping in the middle. If n is the number of flagella at one end of the cell and 2n the number of overlapping flagella in the middle of the cell, then the characteristic array is n:2n:n (e.g., 10:20:10 or 300:600:300). The coated membranes, distinctive cytoplasmic structures (including the sillon, a cell-length invagination or groove of the outer membrane in contact with the inner membrane), and relative proportions that distinguish these genera are depicted in Fig. 2, based on the morphometric analyses summarized in Table 1. The habitats of these organisms are predictable (e.g., the crystalline style of bivalve mollusks for Cristispira and the intestine of dry woodeating cockroaches and termites for the others). None has been grown axenically. As molecular biological data are not yet available, species have been determined morphologically. Five species of large, symbiotic spirochetes have been described in the modern bacteriological literature and reverified, revised, or named as: Clevelandina reticulitermitidis, Cristispira pectinis, Diplocalyx calotermitidis, Hollandina pterotermitidis, and Pillotina calotermitidis. (For genera description, including an explanation of the morphometric analysis of spirochetes, see Bermudes et al., 1988.) Although often classified on the basis of size and light microscopic morphology in the family This chapter was taken unchanged from the second edition.
Spirochaetaceae (e.g., Bermudes et al., 1988), these spirochetes are ultrastructurally distinct from all other members of the Spirochaetaceae (see Free-Living Saccharolytic Spirochetes: The Genus Spirochaeta in this Volume). Therefore, we classify the large symbiotic spirochetes in the family Pillotinaceae. (This family was first suggested by Hollande and Gharagozlou, 1967, who used the incorrect Latin derivative “Pillotaceae.”) The spirochetes most similar morphologically to any member of the Pillotinaceae are the tick-borne symbionts, e.g., Borrelia persica, (flagella formula 25:50:25) (Karimi et al., 1979); the free-living microbial mat spirochete Mobilifilum chasei (10:20:10) (Margulis et
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