[Biodegradation of Polyethylene Microplastic: A Review].

Over the recent decades, global plastic production has grown dramatically due to the huge demands of consumption. As a consequence, large amounts of plastic waste have accumulated in the environment and will be cleaved into microplastics. Due to the low bioavailability, the microplastics will exist in the environment persistently and cause massive environmental stress. Plastic pollution is currently one of the biggest environmental concerns. Recent studies have shown the possibility to obtain degrading microorganisms of microplastics from the natural environment. Some microorganisms can break down microplastics into water and carbon dioxide. This paper reviewed the current research on biodegradation of polyethylene (PE), which is the most abundant microplastic type in the environment, and discussed the quantification methods of the degradation effect. Given that current biodegradation efficiency is relatively limited, further research is required.

Robust host source tracking building on the divergent and non-stochastic assembly of gut microbiomes in wild and farmed large yellow croaker.

BACKGROUND: Given the lack of genetic background, the source tracking unknown individuals of fish species with both farmed and wild populations often cannot be robustly achieved. The gut microbiome, which is shaped by both deterministic and stochastic processes, can serve as a molecular marker of fish host source tracking, particularly as an alternative to the yet-to-be-established host genetic marker. A candidate for testing the feasibility is the large yellow croaker, Larimichthys crocea, which is carnivorous and ranks the top mariculture fish in China. Wild resource of this fish was depleted decades ago and might have potential problematic estimation because of escaping of farmed individuals. RESULTS: The rectums of wild (n = 212) and farmed (n = 79) croakers from multiple batches were collected for the profiling of their gut bacterial communities. The farmed individuals had a higher alpha diversity and lower bacterial load than the wild individuals. The gut microbiota of the two sources exhibited divergence and high inter-batch variation, as featured by the dominance of Psychrobacter spp. in the wild group. Predicted functional capacity of the gut microbiome and representative isolates showed differences in terms of host source. This difference can be linked to the potential diet divergence between farmed and wild fishes. The non-stochastic distribution pattern of the core gut microbiota of the wild and farmed individuals supports the feasibility of microbiota-based host source tracking via the machine learning algorithm. A random forest classifier based on the divergence and non-stochastic assembly of the gut microbiome was robust in terms of host source tracking the individuals from all batches of croaker, including a newly introduced batch. CONCLUSIONS: Our study revealed the divergence of gut microbiota and related functional profiles between wild and farmed croakers. For the first time, with representative datasets and non-stochastic patterns, we have verified that gut microbiota can be robustly applied to the tracking of host source even in carnivorous fish. Video abstract.

Genome sequence of benzo(a)pyrene-degrading bacterium Novosphingobium pentaromativorans US6-1.

Novosphingobium pentaromativorans US6-1 showed a good ability to degrade high-molecular-weight polycyclic aromatic hydrocarbons. We report the draft genome sequence of strain US6-1, which contains a main chromosome (5,096,413 bp, G+C content of 63.1%) and two plasmids (188,476 and 60,085 bp). The majority of the aromatic-hydrocarbon-degrading genes are encoded in the larger plasmid.

Sphingomonas polyaromaticivorans sp. nov., a polycyclic aromatic hydrocarbon-degrading bacterium from an oil port water sample.

A bacterial strain (B2-7(T)) capable of degrading a wide range of polycyclic aromatic hydrocarbon compounds (2-4 rings) was isolated from a water sample taken from Botan Oil Port in Xiamen, China. The isolate was Gram-negative, short-rod-shaped, aerobic, non-motile and formed yellow-pigmented colonies on LB medium. Cells of strain B2-7(T) were catalase-positive and oxidase-negative. Optimal growth of strain B2-7(T) was observed at pH 7.0, at 26 °C and in 0.5 % NaCl. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain B2-7(T) grouped with members of the genus Sphingomonas and it showed 16S rRNA gene sequence similarity of 95.40 % to Sphingomonas yunnanensis YIM 003(T). The major polar lipids were phosphatidylethanolamine, phosphatidylcholine and sphingoglycolipid. Q-10 and sym-homospermidine were the predominant ubiquinone and polyamine components, respectively. The major fatty acids were C(18:1)ω7c (67.2 %), C(14:0) 2-OH (10.0 %) and C(16:0) (9.6 %). The G+C content of the genomic DNA was 61.8 mol%. Based on phenotypic properties, and phylogenetic and genomic data, strain B2-7(T) represents a novel species of the genus Sphingomonas within the class Alphaproteobacteria, for which the name Sphingomonas polyaromaticivorans sp. nov. is proposed. The type strain is B2-7(T) ( = KCCM 42951(T) = JCM 16711(T)).

Contamination and potential biodegradation of polycyclic aromatic hydrocarbons in mangrove sediments of Xiamen, China.

Five stations were established in the Fenglin mangrove area of Xiamen, China to determine the concentrations of polycyclic aromatic hydrocarbons (PAHs) and the numbers of PAH-degrading bacteria in surface sediments. Assessing the biodegradation potential of indigenous microorganisms and isolating the high molecule weight (HMW)-PAH degrading bacteria was also one of the aims of this work. The results showed that the total PAH concentration of sediments was 222.59 ng g(-1) dry weight, whereas the HMW-PAH benzo(a)pyrene (BaP) had the highest concentration among 16 individual PAH compounds. The variation in the numbers of PAH-degrading bacteria was 2.62 x 10(2)-5.67 x 10(4)CFU g(-1) dry weight. The addition of PAHs showed a great influence in increasing the microbial activity in mangrove sediments. A bacterial consortium, which could utilize BaP as the sole source of carbon and energy, and which was isolated from mangrove sediments and enriched in liquid medium for nearly one year degraded 32.8% of BaP after 63 days incubation.