Bacteria Belonging to the Genus Cycloclasticus Play a Primary Role in the Degradation of Aromatic Hydrocarbons Released in a Marine Environment

Abstract

To identify the bacteria that play a major role in the aerobic degradation of petroleum polynuclear aromatic hydrocarbons (PAHs) in a marine environment, bacteria were enriched from seawater by using 2-methylnaphthalene, phenanthrene, or anthracene as a carbon and energy source. We found that members of the genus Cycloclasticus became predominant in the enrichment cultures. The Cycloclasticus strains isolated in this study could grow on crude oil and degraded PAH components of crude oil, including unsubstituted and substituted naphthalenes, dibenzothiophenes, phenanthrenes, and fluorenes. To deduce the role of Cycloclasticus strains in a coastal zone oil spill, propagation of this bacterial group on oil-coated grains of gravel immersed in seawater was investigated in beach-simulating tanks that were 1 m wide by 1.5 m long by 1 m high. The tanks were two-thirds filled with gravel, and seawater was continuously introduced into the tanks; the water level was varied between 30 cm above and 30 cm below the surface of the gravel layer to simulate a 12-h tidal cycle. The number of Cycloclasticus cells associated with the grains was on the order of 10 3 cells/g of grains before crude oil was added to the tanks and increased to 3 ؋ 10 6 cells/g of grains after crude oil was added. The number increased further after 14 days to 10 8 cells/g of grains when nitrogen and phosphorus fertilizers were added, while the number remained 3 ؋ 10 6 cells/g of grains when no fertilizers were added. PAH degradation proceeded parallel with the growth of Cycloclasticus cells on the surfaces of the oil-polluted grains of gravel. These observations suggest that bacteria belonging to the genus Cycloclasticus play an important role in the degradation of petroleum PAHs in a marine environment.An oil spill is one of the most serious disasters that can occur in a marine environment (22,23). In the early stage of an oil spill, the light fraction of the oil evaporates, while the heavier fraction is slowly removed by photooxidation and biodegradation (11). Microorganisms, especially bacteria, play an important role in the biodegradation of the spilled oil (28). However, the growth of oil-degrading bacteria in seawater and the resulting biodegradation of oil in seawater are limited by nutritional requirements (2, 3). Addition of nitrogen and phosphorus fertilizers has been shown to enhance the biodegradation of oil released in a marine environment (21,38,43).Oil is a complex mixture made up of hundreds of compounds, and these compounds are classified into four groups, namely, saturates, aromatics, resins, and asphaltenes (12). Aromatics are the second most abundant hydrocarbons in crude oil. Benzene, naphthalene, and phenanthrene and their alkylsubstituted derivatives represent typical aromatics (47). Although the biodegradation of such simple aromatics as benzene, toluenes, xylenes, naphthalene, and phenanthrene has been extensively characterized (19), the biodegradation of alkyl-substituted polynuclear aromatic hydrocarbons (PAHs) has scarcely bee...

Marine Oil-Degrading Microorganisms and Biodegradation Process of Petroleum Hydrocarbon in Marine Environments: A Review

“…PAHs Cycloclasticus [36,42,43,73] Pyrene Mycobacterium [25,41,72] one basking alkanes and phytane in 21 days was 47.29 and 41.21 %, respectively [64]. Yuan et al also found the degradation rate of branched hydrocarbons was nearly two times than that of n-alkanes hydrocarbons [77].…”

Oceanobacter-related bacteria are important for the degradation of petroleum aliphatic hydrocarbons in the tropical marine environment

“…Most hydrocarbonoclastic bacteria metabolize either aliphatic or aromatic hydrocarbons, although some bacteria such as strains of Pseudomonas (Whyte et al, 1997) and Rhodococcus (Andreoni et al, 2000) have been shown to degrade both types of hydrocarbons. Among hydrocarbonoclastic bacteria, Alcanivorax (Hara et al, 2003;Kasai et al, 2001;Roling et al, 2004;Yakimov et al, 1998Yakimov et al, , 2005 and Cycloclasticus (Dyksterhouse et al, 1995;Kasai et al, 2002a;Maruyama et al, 2003) strains have been identified as key micro-organisms in the degradation of aliphatic and aromatic hydrocarbons, respectively, in marine environments (Harayama et al, 2004). Alcanivorax strains are distributed in natural marine environments around the world .…”

Change in Bacterial Diversity After Oil Spill in Argentina

“…Another characteristic of marine environments is that the vast majority of bacteria (90-99%) are uncultivable (Amann et al, 1995); hence, the analysis of microbial communities that contribute to in situ hydrocarbon biodegradation activities has been a challenge to microbiologists (Rollins & Colwell, 1986;Wilkinson 1988 Since the pioneering work on marine bacteria by C.E. ZoBell, many bacterial strains have been isolated from the coastal and oceanic environments; these bacteria, including the genera Alteromonas (Beckman et al, 2008;Ivanova et al, 2004), Aeromonas (Stabili & Cavallo 2004), Alcanovorax (Head et al, 2006;Purkrtova et al, 2010), Bacillus (Oguntoyinbo, 2006), Cycloclasticus (Kasai et al, 2002), Chromobacterium, Flavobacterium, Marinobacter spp., Shewanella (Holt et al, 2005), Microscilla (Lennon, 2007), Micrococcus (Süss et al, 2004), Rhodococcus (Süss et al, 2004), Photobacterium, Planacoccus, Pseudomonas, Pseudoalteromonas, and Vibrios, among other genera, have been considered to be representative of marine bacteria. Many of them have the capacity to use different hydrocarbons (Head et al, 2006, Yu et al, 2005a.…”