A molecular phylogenetic analysis of luxA gene sequences of light organ symbionts of the fish Acropoma japonicum (Acropomatidae) and Siphamia versicolor (Apogonidae) revealed that the sequences were related to those of Photobacterium leiognathi ssp. mandapamensis, which is not known to occur as a light organ symbiont among bioluminescent P. leiognathi clades. The presence of another lux gene element, luxF, coding for nonfluorescent protein, provided additional support for the identity of the light organ symbionts of the fish. Cladogenesis of the light organ symbiont P. leiognathi may be influenced by the radiation of host fishes.

To rapidly identify natural isolates of marine bioluminescent bacteria, we developed amplified ribosomal DNA restriction analysis (ARDRA) methods. ARDRA, which is based on the restriction patterns of 16S rRNA gene digested with five enzymes (EcoRI, DdeI, HhaI, HinfI, RsaI), clearly distinguished the 14 species of marine bioluminescent bacteria currently known, which belong to the genera Vibrio, Photobacterium, and Shewanella. When we applied ARDRA to 129 natural isolates from two cruises in Sagami Bay, Japan, 127 were grouped into six ARDRA types with distinctive restriction patterns; these isolates represented the bioluminescent species, P. angustum, P. leiognathi, P. phosphoreum, S. woodyi, V. fischeri, and V. harveyi. The other two isolates showing unexpected ARDRA patterns turned out to have 16S rRNA gene sequences similar to P. leiognathi and P. phosphoreum. Nevertheless, ARDRA provides a simple and fairly robust means for rapid identification of the natural isolates of marine bioluminescent bacteria, and is therefore useful in studying their diversity.

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Aliivibrio fischeri NCIMB1281T (basonym, Vibrio fischeri) spontaneously started broad-host range vector particle (AfVP) production by budding from the logarithmic phase, and stabilised at around 7.0×10 10 -7.4×10 11 particles mLwithout any accompanying change in the host population. AfVPs had a spherical shape and varied in diameter from 18.1 to 159.2 nm [median±SD, 58.4±11.9 nm, n=528], with 95.1% between 30.2 and 84.6 nm in diameter exhibiting a normal distribution. Their buoyant density and DNA content ranged from 1.3607 to 1.3980 g cm −3 , and 17.3 to 95.3 kbp, respectively. Regardless of UV treatment, AfVPs enhanced the efficiency of plating 116-136% at a multiplicity of infection of ca. 140 in Escherichia coli AB1157. Generalised transduction was observed with a frequency of between 10 −4 and 10 −6 cells per AfVP without UV treatment. Upon infection, the particle membrane remained outside the recipient cell, and a string-like structure coated with a fibrous proteinaceous-like material was present. The growth of the E. coli transductant (AfV-E-trans) reached a maximum of ca. 415% that of the parental E. coli recipient. AfV-Etrans acquired the ability to produce budding particles.