Distribution of nicotinamide phosphoribosyltransferase in genus Aggregatibacter and description of Aggregatibacter animalimorsus sp. nov., Aggregatibacter holmi sp. nov., and Aggregatibacter valvarum sp. nov.

INTRODUCTION

Bacteria of genus Aggregatibacter vary with respect to dependence on exogenous nicotinamide adenine dinucleotide (NAD). The genus is incompletely resolved, as 20% of deposited Aggregatibacter genome sequences do not belong to named species.

METHODS

We performed phenotypic analysis of the four named Aggregatibacter species plus four additional genomospecies, and bioinformatics analysis of 282 genomes; 237 of these genomes represent cultured isolates.

RESULTS

Independence of NAD is ubiquitous in genomospecies related to Aggregatibacter actinomycetemcomitans, common in Aggregatibacter aphrophilus and Aggregatibacter kilianii, and absent from Aggregatibacter segnis plus the six additional genomospecies. Characterised genomospecies qualify for nomenclatural approval according to phenotype and accepted genomic boundaries. Suggested species Aggregatibacter valvarum has clinical relevance, as three of five isolates were cultured from human blood.

CONCLUSION

Naming of three species is proposed. A total of seven named Aggregatibacter species will comprise 87% of deposited genome sequences from cultured strains. The benefit of naming of three other genomospecies is uncertain. Two genomospecies cannot be validly named until in vitro culture has been accomplished.