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Aims:  This paper describes optimization of electrotransformation of Mu transposition complexes into Lactococcus lactis cells and identification of genes affecting nisin production. Methods and Results:  The highest transformation efficiency, 1·1 × 102 transformants μg−1 of input transposon DNA, was achieved when cells were grown to an OD600 of 0·5 in the presence of 1·5% of glycine and treated with 20 μg ml−1 ampicillin for 60 min. Three insertions affecting nisin production, which were identified at nisB, fhuR, and rpiA genes, were screened from a library of ∼2000 erythromycin‐resistant transformants using a nisin bioassay method. NisB is part of the nisin biosynthetic machinery, explaining the loss of nisin production in nisB mutant. FhuR is a transcription regulator involved in sulphur acquisition. Inactivation of fhuR presumably results in a low cellular cystein level, which affects nisin biosynthesis that involves utilization of cystein. RpiA is involved in pentose phosphate pathway and carbon fixation. The rpiA mutant showed reduction in nisin production and slow growth rate. Conclusions:  The results showed that Mu transposition complex mutagenesis can be used to identify genes in L. lactis. Three genes involved in nisin production were identified. Significance and Impact of the Study:  Expanding the Mu transposition‐based mutagenesis to Lactococci adds a new tool for studies of industrially important bacteria.

Abstract. Heavy regional particulate matter (PM) pollution in China has resulted in an important and urgent need for joint control actions among cities. It is advisable to improve the understanding of the regional background concentration of PM for the development of efficient and effective joint control policies. With the increase of height the influence of source emission on local air quality decreases with altitude, but the characteristics of regional pollution gradually become obvious. A method to estimate regional background PM concentration is proposed in this paper, based on the vertical characteristics of periodic variation in the atmospheric boundary layer structure and particle mass concentration, as well as the vertical distribution of particle size, chemical composition and pollution source apportionment. According to the method, the averaged regional background PM2.5 concentration in July, August and September 2009, being extracted from the original time series in Tianjin, was 40 ± 20, 64 ± 17 and 53 ± 11 μg m−3, respectively.

Zn x ͑ZnO͒ 1−x granular films with nominal atomic concentration of x =0ϳ 1 were prepared by magnetron cosputtering method. Ferromagnetism is observed in films with 0.04Յ x Ͻ 0.60. The room-temperature saturated magnetization increases with increasing x and reaches its maximum value of about 3.34 emu/cc at x = 0.31. The temperature-dependent magnetization curve could be fitted within the framework of Stoner model in a large temperature range from 50 to 800 K. The obtained Curie temperature is higher than 500°C. It is found that the main point defects in ZnO are Zn interstatial and oxygen vacancy. Room-temperature photoluminescence analysis and high-temperature x-ray diffraction measurement show conclusive evidence that the native point defect of Zn interstitial plays a crucial role in the observed magnetic behaviors. By implicating the shallow donor related carriers and/or extending the charge-transfer mechanism to metal/semiconductor heterostructure, the result could be qualitatively explained based on the Stoner theory of band magnetism. These findings may help to get further insight into the ferromagnetic origin in nonmagnetic ion doped ZnO systems.