Production of a chloramphenicol-resistant mutant of Lysinibacillus sphaericus by solid state fermentation

A highly active mosquitocidal mutant of Lysinibacillus sphaericus Ahmed 2362, namely, UCR-146, was efficiently produced on cottonseed meal (CSM) medium, using sand as a carrier under solid state fermentation (SSF). The optimum CSM concentration for the highest sporulation and toxin formation was 12%. The maximum toxicity of the tested organism against second instar larvae of Culex pipiens was obtained at 25% moisture content, initial pH 6–7, 1% sodium acetate, 18.9×10⁶ CFU/g inoculum and 6 days incubation period at 30°C. Pilot scale production of UCR-146 under the optimum SSF conditions was assessed in aluminium trays. Spore count, mortality of larvae and LC₅₀ of the final product were 5.5×10¹⁰ CFU/g, 72% at 1 part per million (PPM) and 0.54 PPM, respectively. These results were comparable with those obtained from bench-scale production (in flasks). The cost of 1 kg of this bio-larvicide was estimated at US $0.34.     

Tetrasporangia and gametangia on the same thallus in the red algae Cystoclonium purpureum (Huds.) Batt. and Chondria baileyana (Mont.) Harv.

The occurrence of cystocarps and tetrasporangia on the same thallus is reported in Chondria baileyana (Mont.) Harv. and Cystoclonium purpureum (Huds.) Batt. var. purpureum. Spermatangia and tetrasporangia on the same plant were also noted in C. purpureum var. cirrhosum Harv.     

IrCL1 - the haemoglobinolytic cathepsin L of the hard tick, Ixodes ricinus

Intracellular proteolysis of ingested blood proteins is a crucial physiological process in ticks. In our model tick, Ixodes ricinus, cathepsin L (IrCL1) is part of a gut-associated multi-peptidase complex; its endopeptidase activity is important in the initial phase of haemoglobinolysis. We present the functional and biochemical characterisation of this enzyme. We show, by RNA interference (RNAi), that cathepsin L-like activity that peaks during the slow feeding period of females is associated with IrCL1. Recombinant IrCL1 was expressed in bacteria and yeast. Activity profiling with both peptidyl and physiological protein substrates (haemoglobin and albumin) revealed that IrCL1 is an acidic peptidase with a very low optimum pH (3-4) being unstable above pH 5. This suggests an endo/lysosomal localisation that was confirmed by indirect fluorescence microscopy that immunolocalised IrCL1 inside the vesicles of digestive gut cells. Cleavage specificity determined by a positional scanning synthetic combinatorial library and inhibition profile indicated that IrCL1 has the ligand-binding characteristics of the cathepsin L subfamily of cysteine peptidases. A non-redundant proteolytic function was demonstrated when IrCL1-silenced ticks had a decreased ability to feed compared with controls. The data suggest that IrCL1 may be a promising target against ticks and tick-borne pathogens.     

Transformation of carbonate minerals in a cyano-bacterial mat in the course of laboratory modeling

A laboratory model of a cyano-bacterial mat with mineral layers of carbonates was used to examine the dynamics of the transformation of calcium-magnesium carbonate under the conditions of a soda lake. The activity of various organisms of the cyanobacterial community results in conditions under which the Ca-Mg carbonate precipitate undergoes changes. The crystal lattice of the initial carbonate is restructured; its mineralogical composition changes depending on the conditions of the mat. In magnesium calcites, which are formed under such low-temperature conditions, a rudimentary cation adjustment can occur with the formation of dolomite domains. These experiments confirm the hypothesis that the dolomite found in stromatolites is of a secondary origin and can be formed in the course of transformation of Ca-Mg carbonates under alkaline conditions in an alkaliphilic cyanobacterial community.     

Assessment of Lead Ecotoxicity in Water using the Amphibian Larvae (<Emphasis Type="BoldItalic">Xenopus laevis</Emphasis>) and Preliminary Study of its Immobilization in Meat and Bone Meal Combustion Residues

Lead (Pb) is a major chemical pollutant of the environment. It has been associated with human activities for the last 6000 years. Quite rightly, it remains a public health concern today. The present investigation evaluates the toxic potential of Pb in larvae of the toad Xenopus laevis after 12 days exposure in lab conditions. Acute toxicity, genotoxicity and Pb bioaccumulation were analyzed. The genotoxic effects were analyzed in the circulating blood from the levels of micronucleus induction according to the French standard micronucleus assay (AFNOR 2000 Association française de normalization. Norme NFT 90-325. Qualité de l’Eau. Evaluation de la génotoxicité au moyen de larves d’amphibien (Xenopus laevis, Pleurodeles waltl)). Lead bioaccumulation was analyzed in the liver of larvae at the end of exposure. Moreover, the toxic potential of lead, in aquatic media, was investigated in the presence of meat and bone meal combustion residues (MBMCR) known to be rich in phosphates and a potential immobiliser of lead. Previously, acute toxicity and genotoxicity of MBMCR alone were evaluated using Xenopus larvae. The results obtained in the present study demonstrated: (i) that lead is acutely toxic and genotoxic to amphibian larvae from 1 mg Pb/l and its bioaccumulation is significant in the liver of larvae from the lowest concentration of exposure (1 μg Pb/l), (ii) MBMCR were not acutely toxic nor genotoxic in Xenopus larvae, (iii) lead in presence of MBMCR induced inhibition or reduction of the toxic and genotoxic potential of lead in water at concentrations that do not exceed the capacity of MBMCR of Pb-binding (iv) Pb accumulation in larvae exposed to lead with MBMCR in water was lower than Pb-accumulation in larvae exposed to lead alone except at the concentration of 0.01 mg Pb/l suggesting complex mechanisms of MBMCR interaction in organisms. The results confirm the high toxicity and genotoxicity of lead in the aquatic compartment and suggest the potential utility of MBMCR for use in remediation.     

模拟放牧干扰对黄土丘陵区生物结皮坡面土壤水分入渗的影响

水分是黄土高原地区植被恢复的关键影响因子,该区广泛分布的生物结皮显著影响土壤水分入渗。干扰影响生物结皮土壤水分入渗,但目前不同强度的干扰对生物结皮土壤水分入渗的影响仍不明确。本研究以黄土丘陵区吴起县合沟小流域的生物结皮坡面为对象,模拟羊蹄踩踏干扰,研究10%、20%、30%和40%干扰强度(以生物结皮破损度表征)对生物结皮坡面地表覆被的影响,采用线源入流入渗法观测了不同强度干扰后土壤水分入渗特征,通过结构方程模型和相关性分析,探索了干扰对生物结皮坡面土壤水分入渗的影响机制。结果表明:与对照(不干扰)相比,10%干扰强度下藻结皮盖度显著增加33.6%,20%干扰强度对藻结皮盖度无显著影响,30%和40%干扰强度下藻结皮盖度分别显著降低了36.1%和75.0%;40%干扰强度显著增加了枯落物盖度(34.3%),其他处理无显著影响;10%、20%和30%干扰强度下地表粗糙度分别显著降低了22.3%、11.1%和5.6%,40%干扰强度下增加了8.2%;40%干扰强度下初始入渗率显著增加了77.1%,其他干扰强度无显著影响;不同干扰对土壤稳定入渗率和平均入渗率无显著影响。可见,干扰主要通过降低藻结皮盖度,增加枯落物盖度和改变地表粗糙度,进而促进了土壤水分初始入渗。本研究可为黄土高原退耕地生物结皮管理提供科学依据。     

Correlation among clock gene expression rhythms,sleep quality,and meal conditions in delayed sleep-wake phase disorder and night eating syndrome

Clock genes that comprise the circadian clock system control various physiological functions. Delayed sleep-wake phase disorder (DSWPD) and night eating syndrome (NES) are characterized by delayed sleep and meal timing, respectively. We estimated that clock gene expression rhythms in DSWPD patients may be delayed in comparison with the healthy subjects due to delayed melatonin secretion rhythms, producing eveningness chronotype in these individuals. However, it was difficult to estimate which clock gene expression rhythms were delayed or not in NES patients, because previous studies revealed that melatonin secretion rhythm was a little delayed compared with healthy individuals and that chronotype of NES patients depended on the individuals. Therefore, we examined expression rhythms of clock genes such as Period3 (Per3), nuclear receptor subfamily 1, group D, member 1 (Nr1d1) and Nr1d2 in these patients. Further, we expected sleep and meal patterns in DSWPD and NES patients may be more diverse than patterns observed in healthy subjects, and thus analyzed relationships among clock gene expression rhythms, sleep quality, sleep midpoint time, and meal times. We enrolled healthy male participants along with DSWPD and NES male patients, and asked all participants to answer questionnaires and to keep diaries to record information on their sleep and meals. Further, we asked them to collect 5–10 beard follicle samples, 6 times every 4 h. We measured clock gene expression rhythms using total RNA extracted from beard follicle cells. Peak time of clock gene expression in the NES group showed more diversity than the other groups, and that in the DSWPD group was delayed compared with the control group. In addition, the peak time of clock gene expression was negatively correlated with sleep quality and positively correlated with meal time after a long fast. Amplitudes of clock gene expression, especially Per3, positively responded to better mental and physical conditions as well as with better sleep quality. Results of this study suggest that peak times of clock gene expression in NES patients depended on the individuals; some patients with NES showed similar clock gene expression rhythm to healthy subjects, and other patients with NES showed similar to DSWPD patients. Moreover, this study suggests that meal time after a long fast may influence more determination in clock gene expression rhythms than the time of breakfast. Therefore, this study also indicates that Per3 clock gene may be one of the parameters that will help us understand sleep and meal rhythm disturbances.     

Black soldier fly defatted meal as a dietary protein source for broiler chickens: effects on carcass traits,breast meat quality and safety

Finding insect meals as alternative sources of poultry feedstuffs is a recent research topic; therefore, the present study aimed to evaluate the effects of defatted black soldier fly (Hermetia illucens L., HI) larvae meal in broiler chicken diets on the carcass characteristics and meat quality parameters, proximate composition, fatty acid profile and the heavy metal content of the breast meat. Four dietary treatments were designed: a control diet (HI0) and three experimental diets (HI5, HI10 and HI15), corresponding to 50, 100 and 150 g/kg HI inclusion levels, respectively. The inclusion of 50, 100 and 150 g HI meal per kg feed supply 16.56%, 33.01% and 49.63% of required crude protein. The broilers were slaughtered at day 35, the carcasses were weighed and the breast muscles were excised from 16 birds per each feeding group (two birds per replicate pens) and used for meat quality evaluation. Linear and quadratic responses were observed, for increasing HI meal levels, in the live and carcass weights (maximum for HI10). As far as the colour of the breast meat is concerned, redness (a*) showed a linear response, while yellowness (b*) linearly decreased with increasing HI meal levels (minimum for HI15). As the HI larvae meal increased in the diets, the moisture content linearly decreased and the protein content increased. The total saturated fatty acid and total monounsaturated fatty acid proportions rose to the detriment of the polyunsaturated fatty acid fraction. The HI larvae meal, used in the current study, represents a valuable protein source for broiler chickens when included by up to 100 g/kg in their diets, as an improved slaughtering performance was observed without any detrimental effects on meat quality parameters or heavy metal residues in the meat.     

Development of reproducible assays for polygalacturonase and pectinase

Polygalacturonase and pectinase activities reported in the literature were measured by several different procedures. These procedures do not give comparable results, partly owing to the complexity of the substrates involved. This work was aimed at developing consistent and efficient assays for polygalacturonase and pectinase activities, using polygalacturonic acid and citrus pectin, respectively, as the substrate. Different enzyme mixtures produced by Aspergillus niger and Trichoderma reesei with different inducing carbon sources were used for the method development. A series of experiments were conducted to evaluate the incubation time, substrate concentration, and enzyme dilution. Accordingly, for both assays the recommended (optimal) hydrolysis time is 30 min and substrate concentration is 5 g/L. For polygalacturonase, the sample should be adjusted to have 0.3–0.8 U/mL polygalacturonase activity, because in this range the assay outcomes were consistent (independent of dilution factors). Such a range did not exist for the pectinase assay. The recommended procedure is to assay the sample at multiple (at least 2) dilution factors and determine, by linear interpolation, the dilution factor that would release reducing sugar equivalent to 0.4 g/L d-galacturonic acid, and then calculate the activity of the sample accordingly (dilution factor × 0.687 U/mL). Validation experiments showed consistent results using these assays. Effects of substrate preparation methods were also examined.     

Earlier and warmer springs increase cyanobacterial (Microcystis spp.) blooms in subtropical Lake Taihu,China

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