Actinomycetes University of Udine, Mycology Department ISSN: 0732-0574 Vol. 3, Num. 2, 1992

ACTINOMYCETE SYSTEMATICS SUBCOMMITTEES 1990-1998

A.J. MCCARTHY

Department of Genetics and Microbiology, University of Liverpool, Liverpool L69 3BX, U.K.

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In short, the subcommittee structure of the International Committee of Systematic Bacteriology (ICSB) is undergoing extensive revision as reported in the minutes of the committee's meeting in Osaka, Japan in September 1990 (Int. J. Syst. Bacteriol., 41: 188-189). Two ad hoc working parties each consisting of five members, are to recommend proposals for reform.

Actinomycete taxonomists responded swiftly and at the Osaka meeting, set up the Subcommittee on the Systematics of Actinobacteria (Int. J. Syst. Bacteriol., 41: 399). This is to be an umbrella for 9 groups taking on the previous responsibilities of the Subcommittees on: Actinomycetales; Corynebacterium and Coryneform bacteria; Nocardia and Related Organisms. The membership of these pre-Osaka subcommittees have by now given their views on the reorgani- sation and offered their services to one or more of the nine groups, up to a maximum of three for any one individual. These groups, now subcommittees themselves, are charged with the task of producing minimum descriptive standards for the taxa assigned to them "along phylogenetic lines" and having achieved this within the allotted eight years, will cease to exist.

The Actinomycetales Subcommittee comprised eighteen members and I served as their secretary from 1988-1990. Throughout the 1980s at least, the production of minimum descriptive standards was the most tangible responsibility of this subcommittee and probably all others within ICSB. Indeed, Dr. Tom Cross as acting secretary in 1982 circulated requests for minimum descriptions for genera, accompanied by guidelines for producing these, to appropriate individuals engaged in taxonomic research on actinomycete genera. Many minimum descriptions were received but their collation and submission to ICSB never took place, probably because the process was overtaken by events. This is clear from the minutes of the Actinomycetales Subcommittee meeting in Manchester,U.K. in September 1986 (Int. J. Syst. Bacteriol., 37: 88-90) where it was noted that "most members of the Subcommittee had been involved as editors, advisers, authors or referees for Volumes 2 and 4 of Bergey's Manual of Systematic Bacteriology, 9th Edition. This work complemented and extended the Subcommittee's work on producing minimal standards for descriptions of new taxa". When Dr. David Labeda became chairman of the subcommittee in 1988, we continued this theme and resolved to abstract minimum descriptions from Volume 4 of Bergey's Manual, 9th Edition for circulation to, and modification by, subcommittee members and other actinomycete taxonomists. We would have been ably as- sisted by the imminent publication of Bergey's Determinative Manual and the second edition of The Prokaryotes. Again, the production of minimum descriptive standards for actinomycete taxa has been overtaken by events, on this occasion, the introduction of a complex subcommittee structure to achieve that end by 1998.

The reform of ICSB subcommittees did however have another primary aim: the rationalisation of phylogenetic and phenetic approaches to bacterial systematics. With this in mind, a phylogenetic subcommittee is to be set up. Also, phylogeny has been used by the Subcommittee on the Systematics of Actinobacteria as the basis for the suprageneric affiliations within the Actinobacteria and as the means of de- limiting the group as a whole. Ribosomal RNA cataloguing and, more recently, sequencing provide new and valuable insights into the origin and evolution of bacterial taxa and this has exerted its effect on actinomycete taxonomy. Thermoactinomycetes with their stable branching aerial and substrate mycelium, but low Mol % GC ratio and typical bacterial endospore structure, are phylogenetically distant from actinomycetes. While this has now been established for over ten years, there is a distinct impression that actinomycete systematists and their subcommittee(s) have shied away from resolving the nomenclatural implications. Circum- scription of Thermoactinomyces is straightforward, and species diversity appears to be limited and simple to iden- tify, so perhaps this is the reason for a lack of urgency. It is important that the reorganised ICSB subcommittees, driven by the introduction of phylogeny into bacterial systematics, do not lose sight of the distinction between the two objectives of a classification. These can in certain circumstances be contradictory, and are: classification as a description of the natural order; classification as the basis for a reliable system of identification.

One of the criticisms of the Actinomycetales Subcommittee and I presume many others, has been the general lack of response from its members.

Certainly, comments on the reorganisation described above were received from less than 50% of the membership. It is important that some of their comments are recorded here, not least because Dr. Lev. Kalakoutskii asked some time ago, and rightly so, that suggestions be pooled and published here in Actino- mycetes. Dr. Kalakoutskii reiterated the need to consider carefully the concept of taxospecies versus genospecies and the danger of "splitting the roads leading to versus organisms". The need for reorganisation of the subcommittee structure to stimulate activity was supported by all, with a few reservations. Dr. Stan Williams queried the need for such an elaborate system simply to define minimum criteria. Dr. Helmut Prauser agreed with the phylogenetic structure but not the use of the term Actinobacteria to describe it, and offered an alternative subdivision of the new subcommittees on a more pragmatic if taxonomically illogical basis. Finally, Dr. Tom Cross raised again the problem of species identification in Streptomyces and proposed some form of defined interlaboratory cooperation that might work towards a reproducible scheme. I am sure that comments on this point and any other raised in this report will be gratefully received by the Editor.

Copyright 1992 CETA