Abstract Three bacteria isolated for degradation of rubbers were compared for their growth characteristics derived from the Bradford protein assay and turbidity (optical density, OD) measurement. Both Alcaligenes xylosoxidans T2 and Pseudomonas aeruginosa GP10 were fast-growing bacteria while Nocardia corynebac- terioides S3 was a slow grower utilizing rubber as the sole source of carbon and energy, but the extent of degradation was lower by the formers than the lat- ter. A. xylosoxidans T2, P. aeruginosa GP10 and N. corynebacterioides S3 showed a typical sigmoidal growth pattern based on binding of Coomassie Bril- liant Blue G250 to bacterial proteins and spectropho- tometrical measurement at 600 nm. Both assays showed similar growth characteristics for all three bacteria in this study. Degradation of rubber was more pronounced by N. corynebacterioides S3 than either A. xylosoxidans T2 or P. aeruginosa GP10 during 70 days of incubation. Our results suggest that slow- growing bacteria may play a much greater role in degrading polymeric materials than was previously believed. Keywords Bradford assay Æ Coomassie Brilliant Blue-G250 Æ Bacterial growth Æ Polymer deterioration Introduction Bacteria are widely recognized for their abilities in degradation and deterioration of polymeric materials [1–5]. Conventional test methodologies tend to select those microorganisms that are capable of establishing growth quickly in culture medium in the initial enrichment process. Recently, however, results showed that slow-growing bacteria were capable of causing much greater damage to polymeric materials than fast- growing ones given that the investigation was carried out over an extended period of time [6]. The slow- growing bacteria tend to initiate growth slowly first and then surpass the fast-growing ones over time of incu- bation. To further understand the differences between these two groups of apparently different bacteria, it is necessary to evaluate their growth characteristics. Bacterial growth is a very important and useful parameter in many microbiological research and industrial applications. Currently, at least two catego- ries of methods are available for measuring bacterial growth. Direct measurements include both total cell count and viable count while the indirect measurement is based on measurements of turbidity or other chem- ical indicator, e.g., protein content, for bacterial growth [3, 7]. Because total and viable counts are time J.-D. Gu Marine Surface Biology/Environmental Microbiology, Key Laboratory of Tropical Marine Environment Dynamics (LED), South China Sea Institute of Oceanography, Chinese Academy of Sciences, 164 Xingang Road West, Guangzhou 510301, P.R. China L. Pan Æ J.-D. Gu Laboratory of Environmental Microbiolgy and Toxicology, Department of Ecology & Biodiversity, The University of Hong Kong, Pokfulam Road, Hong Kong SAR, P.R. China J.-D. Gu (&) Department of Ecology & Biodiversity, The University of Hong Kong, 3S-11 Kadoorie Biological Sciences Building, Pokfulam Road, Hong Kong SAR, P.R. China e-mail: jdgu@hkucc.hku.hk J Polym Environ (2006) 14:273–279 DOI 10.1007/s10924-006-0016-5 123 ORIGINAL PAPER Comparing the Growth Characteristics of Three Bacteria Involved in Degrading Rubbers Ji-Dong Gu Æ Li Pan Published online: 8 July 2006 Ó Springer Science+Business Media, Inc. 2006