Microbial activities in brine, seawater, or estuarine
mud are involved in iodine cycle. To investigate the
effects of the microbiologically induced iodine on other
bacteria in the environment, a total of 13 bacteria that
potentially participated in the iodide-oxidizing process were
isolated from water or biofilm at a location containing
131 μg ml−
1 iodide. Three distinct strains were further
identified as Roseovarius spp. based on 16 S rRNA gene
sequences after being distinguished by restriction fragment
length polymorphism analysis. Morphological characteristics
of these three Roseovarius spp. varied considerably
across and within strains. Iodine production increased with
Roseovarius spp. growth when cultured in Marine Broth
with 200 μg ml−1 iodide (I−). When 106 CFU/ml Escherichia
coli, Pseudomonas aeruginosa, and Bacillus pumilus
were exposed to various concentrations of molecular iodine
(I2), the minimum inhibitory concentrations (MICs) were
0.5, 1.0, and 1.0 μg ml−1, respectively. However, fivefold
increases in the MICs for Roseovarius spp. were obtained.
In co-cultured Roseovarius sp. IOB-7 and E. coli in Marine
Broth containing iodide (I−), the molecular iodine concentration
was estimated to be 0.76 μg ml−1 after 24 h and less
than 50 % of E. coli was viable compared to that co-cultured
without iodide. The growth inhibition of E. coli was also
observed in co-cultures with the two other Roseovarius spp.
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