Detection of antibiotic resistance and tetracycline resistance genes in Enterobacteriaceae isolated from the Pearl rivers in South China

This study investigated antibiotic resistance profiles and tetracycline resistance genes in Enterobacteriaceae family isolates from the Pearl rivers. The Enterobacteriaceae isolates were tested for susceptibility to seven antibiotics ampicillin, chloramphenicol, ciprofloxacin, levofloxacin, sulphamethoxazole/trimethoprim, tetracycline and trimethoprim. In Liuxi reservoir, with an exception to ampicillin resistant strains (11%) no other antibiotic resistance bacterial strains were detected. However, multiple drug resistance in bacterial isolates from the other sites of Pearl rivers was observed which is possibly due to sewage discharge and input from other anthropogenic sources along the rivers. Four tetracycline resistance genes tet A, tet B, tet C and tet D were detected in the isolates from the rivers. The genes tet A and tet B were widely detected with the detection frequencies of 43% and 40% respectively. Ciprofloxacin and levofloxacin resistant enteric bacteria were also isolated from the pig and duck manures which suggest a wider distribution of human specific drugs in the environment. This investigation provided a baseline data on antibiotic resistance profiles and tetracycline resistance genes in the Pearl rivers delta.     

Functional gene expression of oil-degrading bacteria resistant to hexadecane toxicity

Contamination with oil poses a threat to the environment and to human health worldwide. Biological methodologies have proved to be economical, versatile and efficient for the remediation of pollutants. In this paper, a highly efficient oil-degrading bacterial strain USTB-2 was isolated from an oil production well of Dagang oil field in Tianjin, China. The 16S rRNA sequence of USTB-2 showed 100% similarity with that of Bacillus subtilis BSn5. Hexadecane is one of the most important components in petroleum. The half inhibitory ratio (IC₅₀) of hexadecane inhibited organisms, determined by microcalorimetry, was lower in USTB-2 than in B. BSn5. The results indicate that the strain USTB-2 degrades hexadecane to make it less toxic compared with the normal strain. RT-PCR was used to evaluate the expression of oil-degrading enzymes, specifically 4-hydroxyphenylacetate 3-monooxygenase genes (HPMO). A sharp increase in the expression of HPMO genes was observed for USTB-2, while the expression of HPMO genes in reference strain B. BSn5 remained relatively stable. These methods can be used to study the metabolic potential of microorganisms for in situ oil decontamination.     

低温电阻加热对土壤多环芳烃去除和细菌群落的影响

针对电阻加热技术修复多环芳烃污染土壤存在能耗高、降低土壤功能性的问题,采用低温条件 (80 ℃) 的电阻加热以降低能耗、减少对土壤肥力和细菌群落的影响。利用自主研制的电阻加热装置,探究低温加热对土壤多环芳烃的去除效果、对土壤理化性质和细菌群落的影响。结果表明,在80 ℃加热180 min条件下,电阻加热对土壤多环芳烃的去除率为21.8%,苯并[a]蒽、苯并[b]荧蒽、苯并[k]荧蒽、䓛、二苯并[a,h]蒽、茚并[1,2,3-cd]芘和萘的质量分数均低于《土壤环境质量建设用地污染风险管控标准 (试行) 》 (GB 36600-2018) 第一类用地筛选值;电阻加热处理后细菌丰度增幅达108%,提高了群落丰富度和多样性,富集了多环芳烃降解菌和功能基因,将厚壁菌门PAHs降解菌的相对丰度放大了近10倍,提高了编码4,5-二羟基邻苯二甲酸酯脱羧酶 (K04102) 和1,4-二羟基-2-萘甲酰-CoA硫酯酶 (K12073) 的功能基因预测丰度,且不会对土壤肥力水平造成负面影响。本研究结果可为低温电阻加热在多环芳烃污染土壤修复中的应用提供参考。     

利用醋糟生物纯化木质素新策略的效能评估

木质素是醋糟的重要组成部分,是自然界中可直接提供芳香环结构物质的可再生资源,具有广泛的用途。然而,醋糟中木质纤维素结构稳定且难以破坏,限制了木质素的生物分离纯化效率,进而影响了醋糟的资源化利用。针对此问题,设计了一种新的木质素生物分离纯化策略,将混合真菌发酵与厌氧消化处理相结合,借助不同功能微生物的协同作用,在有效破坏木质纤维素结构的同时充分降解多糖。结果表明,经过处理后,醋糟中纤维素和半纤维素的降解率达到了87.65%和96.34%;木质素的纯度达到了62.32%,回收率为76.01%。醋糟中木质纤维素结构被破坏,从而导致体系中水解酶活性的提高。包含GH43、CE1、GH13等碳水化合物活性酶基因的微生物的大量富集是该方法实现木质素高效纯化的根本原因。本研究结果可为醋糟的资源化利用提供参考。     

NH2OH与NO2−对anammox体系中N2O排放的影响

厌氧氨氧化(anammox)为新型生物脱氮工艺,面临N₂O温室气体排放问题。羟胺(NH₂OH)与亚硝酸盐 (NO₂⁻) 是影响anammox体系N₂O排放的重要环境因子。基于批次实验,考察了不同质量浓度NH₂OH和NO₂⁻对anammox体系中N₂O释放的影响。结果表明,在[NO₂⁻]为100~300mg·L⁻¹条件下,N₂O排放量随NH₂OH质量浓度递增;而当[NO₂⁻]增至300~500 mg·L⁻¹,投加高质量浓度NH₂OH(30、50 mg·L⁻¹)能抑制N₂O的产生。微生物群落多样性分析表明,低[NO₂⁻]的环境中,NH₂OH会增加体系中异养菌的相对丰度,并抑制anammox菌的生长;而在高[NO₂⁻]的环境中,高质量浓度的NH₂OH可促进anammox菌与共存异养细菌的生长。功能基因分析表明,N₂O的排放量受到硝化、反硝化及硝酸盐异化还原产铵(DNRA)代谢途径调控,并与norB、nrfA基因丰度呈显著正相关(P<0.05 ) 。因此,anammox体系N₂O产量受到NO₂⁻与NH₂OH综合作用的影响,当进水[NO₂⁻]较高时可通过投加适量NH₂OH降低N₂O排放量,而当进水NO₂⁻不足时可通过抑制NH₂OH的累积量以减少N₂O的生成。该研究结果可为anammox工艺的低碳运行提供参考。     

Genotypic characterization of quinolone resistant-Escherichia coli isolates from retail food in Morocco

This study was conducted to assess the retail food as a possible vehicle for antimicrobial resistant, particularly quinolones resistant and pathogenic Escherichia coli. We determined the prevalence and characteristics of nalidixic acid (Nal) resistant E. coli isolates from diverse retail food samples. In all, 70 (28%) of 250 E. coli isolates studied were Nal-resistant E. coli and 91% of these were multi-drug resistant. Plasmid mediated quinolone resistance genes were identified in 32 isolates, including aac(6′)-Ib-cr (n = 16), qnrS1 (n = 11) and qnrB19 (n = 7). Mutations in gyr A and par C genes were detected among 80% of the isolates, and the isolates showed substitution Ser83-Leu and Asp87-Asn in gyrA and Ser80-Ile in parC. In addition, three different gene cassettes were identified (aadA1, aadA7, aac(3)-Id) in 18%. Virulence-associated genes stx1, eae, sfa, hlyA and stx2 were found in six (8%), three (4%), two (3%), three (4%) and three (4%) isolates, respectively. E. coli isolates of phylogenetic group A were dominant (64%, 45/70). Pulsed field gel electrophoresis revealed none epidemiological relationship between these isolates. The results of this work report the higher frequency of Nal-resistant E. coli isolates from Moroccan retail food samples including MDR and pathogenic isolates.     

华中地区水库沉积物重金属抗性基因的赋存特征及影响因素分析

环境中重金属抗性基因(Metal resistance genes,MRGs)的迁移转化作为环境及生态领域的重要研究内容近年来备受关注,但目前环境中重金属是否是MRGs的重要驱动因素则尚不明确.本研究采用宏基因组技术对华中地区水库沉积物MRCs进行了定量,并分析了不同形态重金属在MRGs迁移转化过程中起到的作用.结果 ...     

磁混凝对市政污水中抗生素抗性基因和重金属抗性基因的削减效能

污水中抗性基因给环境和人类健康带来潜在的危害.本研究通过调查市政排口污水磁混凝处理过程中抗性基因绝对含量和相对丰度变化,考察磁分离技术对市政污水中抗性基因的削减效果.结果表明,加入磁种和絮凝剂的一级搅拌和二级搅拌对抗生素抗性基因(ARGs)、重金属抗性基因(MRGs)和可移动遗传元件均有较好地去除效果,但出水中部分抗性基因的绝对含量增加,这可能是由于出水中依然具有较高含量的水平转移元件(int1,2. 00×10¹⁰ copies·mL^-1; int2,1. 91×10⁸ copies·mL^-1; Tn916/1545e,5. 38×10⁸ copies·mL^-1).网络分析和主成分分析结果表明,磁混凝处理过程中ARGs与MRGs呈显著正相关(P <0. 05),城市污水中常规污染物如悬浮物、磷和COD等是影响抗性基因去除效率的重要因子.这些结果表明,磁混凝可通过有效削减污水中常规污染物进而制约抗性基因的传播和转移;但需要关注磁混凝的出水及脱水污泥的...     

土壤改良剂对再生水滴灌根际土壤菌群多样性及病原菌和抗生素抗性基因丰度的影响

基于再生水农业灌溉利用引发的人体健康和环境风险,通过施用土壤改良剂揭示再生水灌溉根际土壤菌群组成与多样性变化特征,并探讨土壤改良剂对根际土壤病原菌和抗生素抗性基因丰度变化的影响规律,对于土壤改良剂的合理施用具有指导意义.采用高通量测序技术和定量PCR检测方法,研究了生物质炭、生物有机肥、腐植酸、松土精和玉米酒糟对再生水滴灌根际土壤细菌群落多样性及特定基因丰度的影响.结果表明,生物质炭处理显著增加根际土壤有机质和总氮含量;生物有机肥处理显著增加EC值和有机质含量;玉米酒糟处理显著增加EC值、总氮和总磷含量（P<0.05）.除生物质炭处理外,其他各处理均能显著降低根际土壤pH （P<0.05）.5种改良剂处理下根际土壤细菌群落组成与多样性在纲和属水平上较相似,但其相对丰度存在差异.α-Proteobacteria、γ-Proteobacteria、Bacteroidia、Actinobacteria、Acidimicrobiia和Anaerolineae为所有处理中的优势菌纲,优势菌属组成包括：Pseudomonas、Sphingobium、Sphingomonas、Cellvibrio、Allorhizobium-Neorhizobium-Pararhizobium-Rhizobium、Flavobacterium和Algoriphagus（相对丰度>1%）.环境因子关联分析表明,根际土壤细菌群落组成与pH、EC、总氮和总磷含量之间存在较强的关联.病原菌与抗生素抗性基因的检出丰度分别在10³~10⁷ copies ·g^-1和10⁴~10⁸ copies ·g^-1.改良剂对病原菌和抗生素抗性基因检出水平存在较大差异,生物有机肥、松土精和玉米酒糟处理均会导致部分抗生素抗性基因丰度显著增加,而腐植酸和玉米酒糟处理下丁香假单胞菌、茄科雷尔氏菌和大肠菌群丰度显著降低（P<0.05）.弓形菌、蜡样芽孢杆菌、成团泛菌和粪拟杆菌与四环素类（tetA、tetB、tetO和tetQ）、磺胺类（sul1）和红霉素类（ermB和ermC）抗性基因丰度存在显著相关性.研究认为监测再生水灌溉下农业环境中病原菌和抗生素抗性基因的同时,也要关注土壤改良剂的合理施用避免加剧生物污染的散播.     

水产养殖尾水中抗生素抗性基因的去除及磺胺类耐药细菌研究

水产养殖环境中抗生素的大量使用促进了抗生素耐药细菌（antibiotic resistant bacteria,ARB）和抗生素抗性基因（antibiotic resistance genes,ARGs）的出现及传播.利用荧光定量PCR分析了浙江省某水产养殖尾水集中处理系统中8种ARGs的分布特征.结果表明,出水中ARGs的绝对丰度降低了0.91个数量级.磺胺类抗性基因（sul1、sul2）在所检测的抗性基因中占主导地位,且绝对丰度在出水中依然维持较高水平(4.94×10⁹、1.79×10⁹copies·L^-1).16S r RNA基因高通量测序结果显示变形菌门、蓝藻门、拟杆菌门、厚壁菌门和放线菌门是优势菌门,变形菌门和绿弯菌门与sul1、sul2和sul3呈显著相关.筛选出一株对磺胺类抗生素具有耐药性的弗氏柠檬酸杆菌,该菌株为条件致病菌,全基因组测序结果显示该菌株共携带了17个ARGs,其中sul1、sul2、tet A、bla_TEM-1等ARGs均位于1个Inc FIB质粒上,质粒图谱揭示了磺胺...