Indole acetic acid and lipopeptide-producing endophytic bacteria from Taxus chinesis: toxicity evaluation of metabolic products

Endophytes play an important role in plant growth and development. Some one can produce auxins, ACCs, iron carriers, and so on to help plants grow and resist unhealthy growth environments. In addition, they can produce certain antimicrobial substances to resist pests and diseases. Among them, Bacillus is the most common beneficial endophytic bacterium in plants. In this paper, 20 IAA-producing strains were screened from endophytic bacteria isolated from Taxus chinensis var. mairei plant tissues by high-performance liquid-chromatography (HPLC). Based on the 20 IAA-producing strains, LC-TOF-MS technology was used to screen lipopeptide-producing Bacillus sp. As a result, three strains (KLBMPTC01, KLBMPTC10, and KLBMPTC29) of Bacillus-producing lipopeptides with abundant contents and species were obtained. According to the situation of the IAA and lipopeptides produced by these strains, KLBMPTC10 was selected as the experimental strain for later toxicological tests. In an Ames test and oral toxicity experiments in mice, we did not detect mutagenicity and other physiological toxicity. This is hoping to provide a theoretical basis for forest resource protection and biofertiliser production therewith.

An Experimental Strain-Based Study on the Working State of Husk Mortar Wallboards with Openings

Rice husks as common agricultural remnants with low density and good thermal conductivity properties have been used in infill walls in the northern area of China. Accordingly, many tests and numerical simulations were conducted to address a difficult issue, the inaccurate estimation on the lateral load-bearing capacity of different types of husk mortar energy-saving (HMES) wallboards. The difficulty has not been overcome so far, implying that the novel methods are anticipated to achieve the accurate estimation. This paper tests the full-scale HMES wallboards with different openings and obtains the strains at the points distributed on the wallboard sides. The experimental strains are modeled as the approximate strain energy values to produce the characteristic parameter of the HMES wallboard’s stressing state. Furthermore, the inherent working state characteristic points of HMES wallboards are revealed from the evolution of the characteristic parameter called as the normalized approximate strain energy sum, leading to the redefinition of the failure loads for the HMES wallboards. Finally, it investigates the stressing state mode evolution of the HMES wallboard around the failure loads. The achieved results provide the reference to the accurate estimation of the bearing capacity of the HMES wallboards.

Translocation of Orally Inoculated Salmonella Following Mild Immunosuppression in Dairy Calves and the Presence of the Salmonella in Ground Beef Samples

ObjectivesThe objective of this study was to determine if immunosuppression altered Salmonella (SAL) translocation from the GI tract subsequently contaminating the carcass during fabrication.Materials and MethodsWeaned Holstein steer calves (n = 20; BW = 102 ± 2.7 kg) received dexamethasone (DEX; n = 10; 0.5mg/kg BW), a synthetic glucocorticoid, or saline (CON; n = 10; 0.5mg/kg BW) for 4 d (from d –1 to d 2) via a jugular catheter prior to oral inoculation of nalidixic acid resistant Salmonella Typhimurium (3.4×106 CFU/animal) via milk replacer on d 0. Fecal swabs were obtained daily to ensure SAL infection. Blood was collected to assess hematological markers of immunosuppression. Upon harvest (d 5), the ileum, cecal content, lymph nodes (ileocecal, mandibular, popliteal and prescapular), and synovial (stifle, coxofemoral, and shoulder) swabs were collected for the isolation of the inoculated strain of SAL. The trim obtained during fabrication was then ground separating both fore and hind quarters of each carcass. Ground beef samples were collected using a random grab method then combined for a composite sample for each fore quarter and each hind quarter for every carcass. The sample were diluted with 225ml of PBSResultsFollowing inoculation, 100% of DEX calves shed the experimental strain of SAL for 5 d, 90% of CON calves shed from d 1 to 3, and 100% of CON calves shed from d 4 to 5. A treatment by tissue interaction (P < 0.01) was observed for SAL in tissues collected at harvest. Greater (P < 0.001) concentrations of SAL were quantified from the cecum of DEX calves (3.86 ± 0.37 log10 CFU) than CON (1.37 ± 0.37 log10 CFU); There was no difference in SAL concentrations between DEX and CON calves in ileal tissue (P = 0.07), nor ileocecal (P = 0.57), mandibular (P = 0.12), popliteal (P = 0.99), or prescapular (P = 0.83) lymph nodes. Salmonella was isolated from the stifle joint of one calf in the CON group; however, SAL was not isolated from any other joint fluids sampled. The prevalence of SAL in the ground beef samples was recovered in 7 of the 80 (8.75%) samples taken. This is important to note as it was 3.3% of swabs collected from the CON treatment and the opportunity exists for stifle joint fluid to come in contact with meat during hind quarter fabrication.ConclusionThe observed data suggests that the grab method for ground beef sampling may not be a correct quantification of overall presence of SAL in a ground beef sample. Therefore, further studies are needed to determine the effectiveness of pathogen sampling methods on ground beef.

Computation Method of Gear Dynamic Response Using Experimental Strain Data and Application in Pitting Fault Analysis

In this paper, A semi-physical method for calculating time varying mesh stiffness and the dynamic response of gear system based on experimental strain data is studied. In a previous work, it was reported that dynamic strain on gear tooth root can be measured under normal operating condition using fiber Bragg Grating (FBG) sensors. This paper aims to compute gear dynamic response using experimental strain data and give an explanation of the fault propagation process. Using the dynamic strain data from FBG sensors, a method for calculating the dynamic response of gear system is proposed. Based on the theory of potential energy and material mechanics, the relationship between the bending strain of the tooth root and the time varying mesh stiffness is established. The time varying mesh stiffness and dynamic response of healthy gear and pitted gear are then calculated respectively. The force transmission during gear mesh under the condition of surface pitting is analyzed. It is concluded that in the case of pitting fault, there will be a significant loss of torque in the power transmission process due to the loss of contact area. It is further inferred that the loss of meshing force andthedecreasing of Hertzian contact stiffness are the major contributing factors for pitting fault. In addition, the semi-analytical method of computing gear dynamic response is validated with experimental study ofacceleration signal in the perspective of dynamic response.

Assembly of Complete Genome Sequences of Negative-Control and Experimental Strain Variants of Staphylococcus aureus ATCC BAA-39 Selected under the Effect of the Drug FS-1, Which Induces Antibiotic Resistance Reversion

Staphylococcus aureus ATCC BAA-39 is the reference organism for a multidrug-resistant Staphylococcus aureus (MRSA) strain that was used to study drug-induced resistance reversion by an iodine-containing nanomolecular complex, FS-1. PacBio sequencing was performed on both the experimental and control strains, followed by genome assembly, variant calling, and DNA modification profiling.