The Blastocaulis-Planctomyces Group of Budding and Appendaged Bacteria

Abstract

Considerable morphological diversity exists among those budding bacteria with prominent acellular (nonprosthecate) appendages discussed here and (as “The genus Planctomyces”) in Chapter 39 of this Handbook. Few of the morphological sorts seen in aquatic samples have ever been enriched in the laboratory, and even fewer have been isolated as axenic cultures. From what is presently known, there is little question but that these bacteria will eventually be assigned to several different genera or even to different higher taxa. Hence, to avoid unwarranted taxonomic implications, we refer to the entire assemblage of these interesting budding and appendaged bacteria as the “Blastocaulis-Planctomyces group”. We have sorted those members of this group observed by us into entities defined in terms of certain morphological diversification elements, a concept laid out elsewhere in this Handbook (Chapter 1). We call these entities “morphotypes” (Schmidt and Starr, 1978, 1979a,b). Our use of these taxonomically noncommittal designations (“Blastocaulis-Planctomyces group” and “morphotypes”) is further justified later in the present chapter (see “Identification”).