New Members of the Family Enterobacteriaceae
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New Members of the Family Enterobacteriaceae J. MICHAEL JANDA
In the last edition of this chapter, Don Brenner (Brenner, 1991) wrote: “They are, nonetheless, important for a variety of reasons. They have innate importance as members of the family, to be compared and contrasted with their relatives, in attempts to define the phenotypic, phylogenetic, and ecological boundaries of the family.” No words better define the current edition of this chapter as the number of genera of Enterobacteriaceae has risen 60%, from 15 to 24 (excluding Raoultella). This current list of 24 genera does not even include such organisms as Alterococcus agarolyticus and Saccharobacter fermentatus, taxa that are not formally discussed in this chapter, although they possess some characteristics associated with the family Enterobacteriaceae (Yaping et al., 1990; Shieh and Jean, 1998). The exponential increase in new genera within the family Enterobacteriaceae has been fueled by molecular biology, including polymerase chain reaction (PCR) technology and 16S (small subunit) rDNA sequencing. This list of genera will no doubt continue to increase. What has resulted from this molecular onslaught is the basic fundamental knowledge that the family Enterobacteriaceae plays a critical role not only in enteric disease of humans and animals, but also as phytopathogens, as insect pathogens, and in industrial processes. Members of the family Enterobacteriaceae can be broadly classified into four main categories for convenience, although a number of these genera clearly overlap into multiple categories (Table 1). Probably the greatest explosion in our knowledge concerning enterobacteria stems from new insight into their role as endosymbionts of insects or of the parasites that feed on insect larvae (Moran and Baumann, 2000). Some genera, such as Photorhabdus and Xenorhabdus, may serve as new delivery vehicles of important bacterial toxins with insecticidal activity, replacing such classic agents as Bacillus thuringiensis (ffrenchConstant and Bowen, 1999). Knowledge of the association that genera, such as Brenneria and Pectobacterium, have with plant diseases contin-
ues to expand as our understanding of their correct taxonomic position becomes apparent. Phlyogenetic analysis has also revealed that some agents, such as Calymmatobacterium granulomatis, the causative agent of the sexually transmitted disease, donovanosis (granuloma inguinale), are actually members of the Enterobacteriaceae. Thus, our knowledge regarding the Enterobacteriaceae and factors regulating molecular evolution of endosymbionts, disease associations in humans, animals, and plants, biological applications, and ecologic niches will continue to expand at a rapid rate for the forseeable future.
Arsenophonus (Androcidium) In 1986, Werren et al. isolated the causative agent (Arsenophonus nasoniae) of the son-killer (sk) trait from infected tissues of the parasitic wasp, Nasonia vitropennis. The sk trait, a sexratio distor
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