Randall R. Carlson

Taxonomy of Corynebacterium Plant Pathogens, Including a New Pathogen of Wheat, Based on Polyacrylamide Gel Electrophoresis of Cellular Proteins†

The known extant plant pathogenic Corynebacterium species were analyzed by polyacrylamide gel electrophoresis of their cellular proteins. The patterns of the protein bands of 13 species and a new corynebacterial wheat pathogen showed seven distinct groups. Five of these groups consisted of only one species each, one group contained four species, and the last group contained the new wheat pathogen and the remaining four species. The pathogens that could not be distinguished by the polyacrylamide gel analysis differed in phenotypic characteristics, including pathogenic specificity. Thus, for these bacteria we propose recognition of the following taxa: Corynebacterium fascians (Tilford) Dowson, Corynebacterium ilicis (Mandel et al.), Corynebacterium tritici (ex Hutchinson) nom. rev., Corynebacterium iranicum (ex Scharif) nom. rev., Corynebacterium rathayi (Smith) Dowson, Corynebacterium flaccumfaciens subsp. flaccumfaciens (Hedges) Dowson, Corynebacterium flaccumfaciens subsp. poinsettiae (Starr and Pirone) comb, nov., Corynebacterium flaccumfaciens subsp. betae (Keyworth et al.) comb, nov., Corynebacterium flaccumfaciens subsp. oortii (Saaltink and Maas Geesteranus) comb, nov., Corynebacterium michiganense subsp. michiganense (Smith) Jensen, Corynebacterium michiganense subsp. nebraskense (Schuster et al.) comb, nov., Corynebacterium michiganense subsp. insidiosum (McCulloch) comb, nov., Corynebacterium michiganense subsp. sepedonicum (Spieckermann and Kotthoff), comb, nov., and Corynebacterium michiganense subsp. tessellarius subsp. nov., the type strain of which is strain 78181 (= ATCC 33566 = PDDCC7221).

Unusual amino acid usage in the variable regions of mercury-binding antibodies

Monoclonal antibodies (mAb) specific for mercuric ions were isolated from BALB/c mice injected with a mercury‐containing, hapten‐carrier complex. The antibodies reacted by enzyme‐linked immunosorbent assay with bovine serum albumin‐glutathione‐mercuric chloride (BSA‐GSH‐HgCl) but not with BSA‐GSH without mercury. Nucleotide sequences from polymerase chain reaction products encoding six of the antibody heavy‐chain variable regions and seven light‐chain variable regions revealed that all the antibodies contained an unpaired cysteine residue in one hypervariable region, which is unusual for murine antibodies. Mutagenesis of the cysteine to either tyrosine or serine in one of the Hg‐binding antibodies, mAb 4A10, eliminated mercury binding. However, of two influenza‐specific antibodies that contain cysteine residues at the same position as mAb 4A10, one reacted with mercury, although not so strongly as 4A10, whereas the other did not react at all. These results suggested that, in addition to an unpaired cysteine, there are other structural features, not yet identified, that are important for creating an appropriate environment for mercury binding. The antibodies described here could be useful for investigating mechanisms of metal‐protein interactions and for characterizing antibody responses to structurally simple haptens. Proteins 1999;37:429–440. ©1999 Wiley‐Liss, Inc.