Metabolism of Members of the Spiroplasmataceae

Abstract

Cell-free extracts from 10 strains of Spiroplasma species were examined for 67 enzyme activities of the Embden-Meyerhof-Parnas pathway, pentose phosphate shunt, tricarboxylic acid cycle, and purine and pyrimidine pathways. The spiroplasmas were fermentative, possessing enzyme activities that converted glucose 6-phosphate to pyruvate and lactate by the Embden-Meyerhof-Parnas pathway. Substrate phosphorylation was found in all strains. A modified pentose phosphate shunt was present, which was characterized by a lack of detectable glucose 6-phosphate and 6-phosphogluconate dehydrogenase activities. Spiroplasmas could synthesize purine mononucleotides by using pyrophosphate (PP,) as the orthophosphate donor. All spiroplasmas except Spiroplusmu floricolu used adenosine triphosphate (ATP) to phosphorylate deoxyguanosine; no other nucleoside could be phosphorylated with ATP by any spiroplasma tested. These results contrast with those reported for other mollicutes, in which PP, serves as the orthophosphate donor in the nucleoside kinase reaction. The participation of ATP rather than PPi in this reaction is unknown in other mollicutes regardless of the nucleoside reactant. Deoxypyrimidine enzyme activities were similar but varied in the reactions involving deamination of deoxycytidine triphosphate and deoxycytidine. All Spiroplasma spp. strains had deoxyuridine triphosphatase activity. Uridine phosphorylase activity varied among strains and is possibly group dependent. As in all other mollicutes, a tricarboxylic acid cycle is apparently absent in Spiroplasma spp. Reduced nicotinamide adenine dinucleotide oxidase activity was localized in the cytoplasmic fraction of all Spiroplusmu species tested. Our assays indicate that the members of the Spiroplasrnataceae are essentially metabolically homogeneous in the highly conserved pathways which we studied, but differ from other mollicutes in several important respects. These differences are of probable phylogenetic significance and may provide tools for recognition of higher taxonomic levels of mollicutes.The metabolism of the wall-less, helical, sterol-requiring members of the Spiroplasmataceae has been little studied. The insect and plant habitats of the spiroplasmas, as their unique phylogenetic position indicates (59), suggested to us that the metabolism of these organisms might differ from that described for other members of the class Mollicutes (10, 17,39,45,55). Identification of such metabolic differences would aid in the characterization, classification, and study of the phylogeny of the spiroplasmas. This information can also identify metabolic steps or loci that are susceptible to chemical modulations that could inhibit the spiroplasmal diseases of corn, citrus, or other plants.Most reports relating to the metabolism of spiroplasmas have concerned nutrition, noting, for example, the presence or absence of acid produced during growth with various sugars (8, 20,43,44,58). Other reports have described optimal growth responses to various additives in formulations of semi...

Catabolism in Mollicutes

“…The intimate association of mollicutes with animal or plant cells enables their dependence on the host for a (Robinson, 1979) and some spiroplasmas (Chang, 1989), though minimal defined media have been developed for only a small number of Mycoplasma strains (Rodwell, 1983). Thus, mollicutes are generally grown in complex media containing high concentrations of serum or in defined media in which the role of the majority of constituents is uncertain.…”

Pyrophosphate-Dependent Enzymes in Walled Bacteria Phylogenetically Related to the Wall-Less Bacteria of the Class Mollicutes

“…PPi-dependent nucleoside kinase has been found in all three orders of the class Mollicutes (18,22), whereas the other three enzymes have been reported only among members of the orders Acholeplasmatales and Anaeroplasmatales (7,17; Petzel et al, in press; this study). The occurrence of multiple PP,-dependent enzymes among the members of the orders Acholeplasmatales and Anaeroplasmatales and the walled phylogenetic relatives and the reported lack of any PPi-dependent enzymes besides PP,-dependent nucleoside kinase among the members of the order Mycoplasmatales support the rRNA sequence analyses that suggest that the acholeplasmas and anaeroplasmas represent the first branch(es) from the walled group (31, 40).…”

Organization and nucleotide sequences of the Spiroplasma citri genes for ribosomal protein S2, elongation factor Ts, spiralin, phosphofructokinase, pyruvate kinase, and an unidentified protein

“…The pjkA gene is 48 min away from the pyk gene, with the rpsB-tsf transcription unit in between (2, 9). Recently, the presence of PFK and PYK in S. citri has been demonstrated (22). The PFK in S. citri is of the ATPdependent form; no pyrophosphate-dependent PFK activity (27).…”