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Zhang P.,Nanjing University | Zhai C.,Nanjing University | Chen R.,Nanjing University | Liu C.,Nanjing University | And 2 more authors.
Ecological Engineering | Year: 2012

The dynamics of the bloom-forming cyanobacterium Microcystis aeruginosa (MA), total bacteria (TB), and the algicidal bacterium Pseudomonas aeruginosa R219 (PaR) in a eutrophic lake was followed from December 2007 to November 2008 by measuring the copy numbers of 16s rRNA genes (CNrG) of each species using a real-time fluorescence quantitative PCR (FQ-PCR) technique. The highest CNrG of MA was observed in July (3.4×10 5copiesmL -1), while those of TB and PaR peaked in May (2.1×10 6copiesmL -1) and August (3.2×10 4copiesmL -1), respectively. A significant relationship was found between the CNrG of MA and biological factors such as the CNrG of PaR, TB, and the ratio of PaR to TB, as well as environmental factors including dissolved nitrogen (DN) and surface water temperature (T) (r 2=0.955, p<0.001), suggesting that the dynamics of the algicidal bacterium PaR and TB, particularly the ratio of PaR to TB, may regulate the abundance of M. aeruginosa. Thus, we suggest that the algicidal bacterium PaR together with T and DN might play important roles in MA bloom formation and outbreaks in freshwater environments. © 2012 Elsevier B.V.

Zhang P.,Nanjing University | Zhai C.,Nanjing University | Wang X.,Nanjing University | Liu C.,Nanjing University | And 2 more authors.
Journal of Applied Phycology | Year: 2013

Cyanobacteria are the dominant bloom-forming species in Lake Taihu. Understanding the competition among algae is important to control strategies for bloom formation and outbreaks in freshwater ecosystems. In this study, we demonstrate that the cyanobacterium Microcystis aeruginosa PCC7820 and the green alga Quadrigula chodatii FACHB-1080 exhibit a strong competitive inhibitory relationship under co-culture conditions, with the latter strain inhibiting the former. Several factors influence the competitive relationship between the two species, including nutrition, temperature, and organic/inorganic compounds. Q. chodatii strongly inhibited M. aeruginosa growth through the inhibition of nitrogen utilization during co-culture. Temperature was also an influential determinant of the competition capacity between the two species under eutrophic conditions: at lower temperatures (15 °C), M. aeruginosa grew better than Q. chodatii, but the difference was not significant (p > 0. 05), whereas at higher temperatures (25 °C, 35 °C), Q. chodatii grew significantly better than M. aeruginosa (p < 0. 05). Furthermore, the Q. chodatii filtrate strongly inhibited the growth of M. aeruginosa. An analysis of the crude extracts of the algae culture filtrates from uni- and co-cultures using gas chromatography mass spectrometry (GC/MS) indicated that algal metabolites, such as dibutyl phthalate and beta-sitosterol, might play a key role in the competition between algae. © 2012 Springer Science+Business Media B.V.

Mao S.,Jiangsu University | Mao S.,The Key Laboratory of Biotechnology for Medicinal Plants of Jiangsu Province | Han Y.,Jiangsu University | Han Y.,The Key Laboratory of Biotechnology for Medicinal Plants of Jiangsu Province | And 9 more authors.
Hereditas | Year: 2012

To further understand the relationships between the SS genome of Sinapis arvensis and the AA, BB genomes in Brassica, genomic DNA of Sinapis arvensis was hybridized to the metaphase chromosomes of Brassica nigra (BB genome), and the metaphase chromosomes and interphase nucleus of Brassica rapa (AA genome) by comparative genomic in situ hybridization (cGISH). As a result, every chromosome of B. nigra had signals along the whole chromosomal length. However, only half of the condensed heterochromatic areas in the interphase nucleus and the chromosomes showed rich signals in Brassica rapa. Interphase nucleus and the metaphase chromosomes of S. arvensis were simultaneously hybridized with digoxigenin-labeled genomic DNA of B. nigra and biotin-labeled genomic DNA of B. rapa. Signals of genomic DNA of B. nigra hybridized throughout the length of all chromosomes and all the condensed heterochromatic areas in the interphase nucleus, except chromosome 4, of which signals were weak in centromeric regions. Signals of the genomic DNA of B. rapa patterned the most areas of ten chromosomes and ten condensed heterochromatic areas, others had less signals. The results showed that the SS genome had homology with AA and BB genomes, but the homology between SS genome and AA genome was clearly lower than that between the SS genome and BB genome. © 2012 The Authors.

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