Molecular determination of oxytetracycline-resistant bacteria and their resistance genes from mariculture environments of China

Aims: To assess the diversity of antibiotic-resistant bacteria and their resistance genes in typical maricultural environments. Methods nand Results: Multidrug-resistant bacteria and resistance genes from a mariculture farm of China were analysed via cultivation and polymerase chain reaction (PCR) methods. Oxytetracycline (OTC)-resistant bacteria were abundant in both abalone and turbot rearing waters, accounting for 3.7% and 9.9% of the culturable microbes. Multidrug resistance was common, with simultaneous resistance to OTC, chloramphenicol and ampicillin the most common resistance phenotype. 16S rDNA sequence analyses indicate that the typical resistant isolates belonged to marine Vibrio, Pseudoalteromonas or Alteromonas species, with resistance most common in Vibrio splendidus isolates. For OTC resistance, tet(A), tet(B) and tet(M) genes were detected in some multidrug-resistant isolates, with tet(D) being the most common molecular determinant. For chloramphenicol resistance, cat II was common, and floR was also detected, especially in marine Pseudoalteromonas strains. Conclusions: There is the risk of multidrug-resistant bacteria contamination in mariculture environments and marine Vibrio and Pseudoalteromonas species serve as reservoirs of specific antibiotic resistance determinants. Significance and Impact of the Study: This paper and similar findings from Korea and Japan indicate the potential for widespread distribution of antibiotic resistance genes in mariculture environments from the East Asian region of the world.

Molecular characterizations of oxytetracycline resistant bacteria and their resistance genes from mariculture waters of China

Oxytetracycline-resistant bacteria were isolated from a mariculture farm in China, and accounted for 32.23% and 5.63% of the total culturable microbes of the sea cucumber and the sea urchin rearing waters respectively. Marine vibrios, especially strains related to Vibrio splendidus or V. tasmaniensis, were the most abundant resistant isolates. For oxytetracycline resistance, tet(A), tet(B) and tet(D) genes were detected in both sea cucumber and sea urchin rearing ponds. The dominant resistance type for V. tasmaniensis-like strains was the combination of both tet(A) and tet(B) genes, while the major resistance type for V. splendidus-like strains was a single tet(D) gene. Most of the sea cucumber tet-positive isolates harbored a chloramphenicol-resistance gene, either cat IV or cat II, while only a few sea urchin tet-positive isolates harbored a cat gene, actually cat IV. The coexistence of tet and cat genes in the strains isolated from the mariculture farm studied was helpful in explaining some of the multi-resistance mechanisms. (c) 2006 Elsevier Ltd. All rights reserved.

Evaluation of the pyrolytic and kinetic characteristics of Enteromorpha prolifera as a source of renewable bio-fuel from the Yellow Sea of China

The pyrolytic and kinetic characteristics of Enteromorpha prolifera from the Yellow Sea were evaluated at heating rates of 10, 20 and 50 degrees C min(-1), respectively. The results indicated that three stages appeared during pyrolysis; dehydration, primary devolatilization and residual decomposition. Differences in the heating rates resulted in considerable differences in the pyrolysis of E. prolifera. Specifically, the increase of heating rates resulted in shifting of the initial temperature, peak temperature and the maximum weight loss to a higher value. The average activation energy of E. prolifera was 228.1 kJ mol(-1), the pre-exponential factors ranged from 49.93 to 63.29 and the reaction orders ranged from 2.2 to 3.7. In addition, there were kinetic compensation effects between the pre-exponential factors and the activation energy. Finally, the minimum activation energy was obtained when a heating rate of 20 degrees C min(-1) was used. (C) 2009 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.

Molecular characterizations of chloramphenicol- and oxytetracycline-resistant bacteria and resistance genes in mariculture waters of China

In order to gain an understanding of the diversity and distribution of antimicrobial-resistant bacteria and their resistance genes in maricultural environments, multidrug-resistant bacteria were screened for the rearing waters from a mariculture farm of China. Both abalone Haliotis discus hannai and turbot Scophthalmus maximus rearing waters were populated with abundant chloramphenicol-resistant bacteria. These bacteria were also multidrug resistant, with Vibrio splendidus and Vibrio tasmaniensis being the most predominant species. The chloramphenicol-resistance gene cat II, cat IV or floR could be detected in most of the multidrug-resistant isolates, and the oxytetracycline-resistance gene tet(B), tet(D), tet(E) or tet(M) could also be detected for most of the isolates. Coexistence of chloramphenicol- and oxytetracycline-resistance genes partially explains the molecular mechanism of multidrug resistance in the studied maricultural environments. Comparative studies with different antimicrobial agents as the starting isolation reagents may help detect a wider diversity of the antimicrobial-resistant bacteria and their resistance genes. (C) 2009 Elsevier Ltd. All rights reserved.

Black carbon and polycyclic aromatic hydrocarbons (PAHs) in surface sediments of China's marginal seas

This study investigates the distribution of black carbon (BC) and its correlation with total polycyclic aromatic hydrocarbons (I PAH) pound in the surface sediments of China's marginal seas. BC content ranges from < 0.10 to 2.45 mg/g dw (grams dry weight) in the sediments studied, and varied among the different coastal regions. The Bohai Bay sediments had the highest BC contents (average 2.18 mg/g dw), which comprises a significant fraction (27%-41%) of the total organic carbon (TOC) preserved in the sediments. In comparison, BC in the surface sediments of the North Yellow Sea, Jiaozhou Bay, East China Sea and the South China Sea is less abundant and accounted for an average of 6%, 8%, 14% and 5%, respectively, of the sedimentary organic carbon pool. The concentration of I PAH pound in the surface sediments ranges from 41 to 3 667 ng/g dw and showed large spatial variations among the sampling sites of different costal regions. The Bohai Bay has the highest I PAH pound values, ranging from 79 to 3 667 ng/g dw. This reflects the high anthropogenically contaminated nature of the sediments in the bay. BC is positively correlated to TOC but a strong correlation is not found between BC and I PAH pound in the surface sediments studied, suggesting that BC and PAHs preserved in the sediments are derived from different sources and controlled by different biogeochemical processes. Our study suggests that the abundance of BC preserved in the sediments could represent a significant sink pool of carbon cycling in China's marginal seas.

ABUNDANCE OF CHEMICAL-ELEMENTS IN CONTINENTAL-SHELF SEDIMENT OF CHINA

For the first time, an element abundance table of China Shelf Sea sediments is published based on 286 samples from the continental shelf of China analyzed for 62 chemical elements. The shelf sediments result from the redistribution of sediments from China over the continental shelf. On the basis of comparison of element abundances among the China shelf samples, hemipelagic Okinawa Trough samples, and pelagic brown clay from the West Pacific, it is clear that each has its own elemental characteristics. Hg anomaly enrichment in Okinawa Trough sediments may be used as an indicator of hydrothermal activity.

PALEOMONSOONS OF CHINA OVER THE LAST 130,000 YEARS - PALEOMONSOON RECORDS

The characteristics of the modern monsoon climate of China may be used as clues for recognizing the records of paleomonsoon climate. The present paper deals primarily with the various paleomonsoon records of the last 130,000 years in the southeast monsoon area. These records mainly come from the following three fields: (i) the historical, (ii) the geological, including loess-paleosol sequence, deserts, lakes, snowlines, timberlines, the phenomena of continental desertization and so on, and (iii) the biological, presented by vegetation a.d mammals. Among these records, the loess-paleosol sequence in the Loess Plateau reflects a climatic history characterized by alternation of two different climatic periods when the Asian winter monsoon and summer monsoon showed pronounced effects on environment, respectively.

PALEOMONSOONS OF CHINA OVER THE LAST 130,000 YEARS - PALEOMONSOON VARIATION

Based upon the effect of land-sea interaction on the paleomonsoon variation and the time series of climatic proxy-indicators, the historical Asian monsoon variation over the last 130,000 and 18,000 years has been reconstructed with an emphasis on the basic characteristics of summer monsoon circulation. The monsoon-climatic cycles and associated model of environmental development over the central and eastern China are proposed and the mechanism of paleomonsoon variation of China preliminarily discussed. The variation of East Asian monsoon circulation should be regarded as a regional result of both solar-radiation changes and the global glacial-interglacial cycles. The episodic uplifting of the Qinghai-Xizang Plateau since the late Miocene has to a large extent controlled the forming and evolution of the paleomonsoon circulation of China.