Contrasting the Pb (II) and Cd (II) tolerance of Enterobacter sp. via its cellular stress responses

Successful application of microorganisms to heavy metal remediation depends on their resistance to toxic metals. This study contrasted the differences of tolerant mechanisms between Pb²⁺ and Cd²⁺ in Enterobacter sp. Microbial respiration and production of formic acid showed that Enterobacter sp. had a higher tolerant concentration of Pb (>1000 mg l⁻¹) than Cd (about 200 mg l⁻¹). Additionally, SEM confirmed that most of Pb and Cd nanoparticles (NPs) were adsorbed onto cell membrane. The Cd stress, even at low concentration (50 mg l⁻¹), significantly enlarged the sizes of cells. The cellular size raised from 0.4 × 1.0 to 0.9 × 1.6 μm on average, inducing a platelet-like shape. In contrast, Pb cations did not stimulate such enlargement even up to 1000 mg l⁻¹. Moreover, Cd NPs were adsorbed homogeneously by almost all the bacterial cells under TEM. However, only a few cells work as ‘hot spots’ on the sorption of Pb NPs. The heterogeneous sorption might result from a ‘self-sacrifice’ mechanism, i.e., some cells at a special life stage contributed mostly to Pb sorption. This mechanism, together with the lower mobility of Pb cations, caused higher microbial tolerance and removal efficiency towards Pb²⁺. This study sheds evident contrasts of bacterial resistance to the two most common heavy metals.     

In situ investigation of allografted mouse HCN4 gene–transfected rat bone marrow mesenchymal stromal cells with the use of patch-clamp recording of ventricular slices

BackgroundRecently, proof-of-concept experiments have shown that genetically modified bone marrow mesenchymal stromal cells (MSCs) carrying hyperpolarization-activated cyclic nucleotide-gated (HCN) channels were able to express the funny current (I_f) in vitro, which played a key role in the process of pacemaker generation for heart rate, and were capable of pacemaker function after transplantation into the host heart. Nevertheless, because of the lack of direct experimental access to the implanted cells in situ, the changes in electrophysiological characteristics and the mechanisms underlying the pacemaker function of engrafted HCN gene–transfected MSCs in vivo remain unclear.Methods and ResultsOn the basis of the improved preparation of ventricular slices, we successfully performed an in situ investigation of allografted mouse HCN4 gene (mHCN4)-transfected rat MSCs (rMSCs) with the use of patch-clamp recording in ventricular slices. We demonstrate that allografted mHCN4-transfected rMSCs survived in the host heart for >4 weeks; that they expressed I_f, which is generated by the mHCN4 channel, with a similar amplitude but greater negative activation compared with parallel cells cultured in vitro; that they did not express optical action potentials or depolarization-activated inward sodium or calcium currents; and that they exhibited a low incidence of gap-junctional coupling with host cardiomyocytes.ConclusionsThis study provides direct experimental access to investigate MSCs after transplantation into the host heart. We propose that mHCN4-transfected rMSCs survived in the host heart with altered electrophysiological characteristics of I_f and were accompanied by a low efficiency of connexin 43 expression at 4 weeks after transplantation, which may affect its pacemaker function in vivo.     

Single dose of synthetic microRNA-199a or microRNA-149 mimic does not improve cardiac function in a murine model of myocardial infarction

Molecular and Cellular Biochemistry - Intramyocardial injection of synthetic microRNAs (miRs) has recently been reported to be beneficial after myocardial infarction (MI). We conducted a randomized...     

Antifouling potentials of eight deep-sea-derived fungi from the South China Sea

Marine-derived microbial secondary metabolites are promising potential sources of nontoxic antifouling agents. The search for environmentally friendly and low-toxic antifouling components guided us to investigate the antifouling potentials of eight novel fungal isolates from deep-sea sediments of the South China Sea. Sixteen crude ethyl acetate extracts of the eight fungal isolates showed distinct antibacterial activity against three marine bacteria (Loktanella hongkongensis UST950701–009, Micrococcus luteus UST950701–006 and Pseudoalteromonas piscida UST010620–005), or significant antilarval activity against larval settlement of bryozoan Bugula neritina. Furthermore, the extract of Aspergillus westerdijkiae DFFSCS013 displayed strong antifouling activity in a field trial lasting 4 months. By further bioassay-guided isolation, five antifouling alkaloids including brevianamide F, circumdatin F and L, notoamide C, and 5-chlorosclerotiamide were isolated from the extract of A. westerdijkiae DFFSCS013. This is the first report about the antifouling potentials of metabolites of the deep-sea-derived fungi from the South China Sea, and the first stage towards the development of non- or low-toxic antifouling agents from deep-sea-derived fungi.     

Lysionotus fengshanensis Yan Liu & D. X. Nong sp. nov. (Gesneriaceae) from Guangxi,China

Lysionotus fengshanensis Yan Liu & D. X. Nong, a new species of Gesneriaceae from Guangxi, China, is described and illustrated. Lysionotus fengshanensis is very similar to L. longipedunculatus (W. T. Wang) W. T. Wang, but differs by the peduncle being 2–4 cm long and purple, corolla campanulate, 2.5–3.0 cm long, 1.5–1.7 cm in diameter at the mouth, filaments slightly geniculate near the middle, apex of filaments with gland and staminodes 3.     

BenA3基因双元载体的初步构建及转化绿僵菌189的初步研究

用XholⅠ和SalⅠ分别双酶切植物表达载体pCAMB IA1300和含有目的基因的pMD19-T-BenA3,定向连接得到重组质粒pCAMB IA1300-BenA3,将其导入农杆菌AGL-1。经PCR鉴定后,得到可用于绿僵菌转化的农杆菌双元载体。采用的预培养时间、菌液浓度、共培养时间、乙酰丁香酮浓度的条件下,进行农杆菌介导绿僵菌的遗传转化,得到可以稳定性遗传的绿僵菌转化子,随机挑选转化子进行苯菌灵抗性基因的PCR扩增表明,绿僵菌转化子含有了苯菌灵抗性基因。该转化体系的建立,将有利于绿僵菌生防功能基因的克隆和作用机制的研究。