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Effects of Oxidative Challenge on Defensive Enzyme and Cofactors Level in Alkalibacterium sp.F26

Jingjing DUAN ; Liming LIU ; Zhaozhe HUA ; Jian CHEN

Microbiology.2008;35(9):1385-1392.

In this paper,a slight halophilic alkaliphile swain,Alkalibacterium sp.F26,which produced high level of intracellular CAT observed in previous research,was selected as a model microbial to explain the responses of this bacterium to oxidative stress.The results indicated that Alkalibacterium sp.F26 had obvious responses to higher concentration (＞1 mmol/L) of H2O2 than that to lower H2O2 (＜1 mmol/L) challenge from the aspects of defensive enzyme synthesis and cofactors level variation.As for catalase production,the activity increased up to 106.54 U/rag protein which was 1.76 fold of the control when cells were challenged by 3 mmol/L H2O2,but its activity only was 1.13 fold when H2P2 was 100 μmol/L.As far as energy state was concerned,ATP production and NAD+ generation were significantly inhibited from 20.55 μmol/L to 17.80 μmol/L and 69.89 μmol/L to 31.77 μmol/L,respectively,leading to the drop of energy charge from 0.77 to 0.68 and the increase of the portion of NADH/NAD+ from 0.08 to 0.41 in the former case.However,these effects were less distinct under lower concentration of H2O2.Except of the condition of 100 μmol/L H2O2,under which the activation of defensive mechanism resulted in an increase of ATE the level of ATP dropped from 22.69 μmol/L of the control to 22.38 μmol/L and 13.70 μmol/L when challenged by 50 μmol/L and 500 μmol/L H2O2.Besides,the concentration of NADH fluctuated and the NAD+ gradually reduced when H2O2 below 1 mmol/L.

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Isolation and Characterization of Antifungal Endophytic Bacteria from Soybean

Shumei ZHANG ; Changqing SHA ; Yuxia WANG ; Jing LI ; Xiaoyu ZHAO ; Xiancheng ZHANG

Microbiology.2008;35(10):1593-1599.

Endophytic bacteria reside in most healthy plants;it can not be easily influenced by outer environment.Some endophytic bacteria are beneficial to host plants,such as growth promotion,disease prevention and nitrogen fixation etc.Therefore,endophytic bacteria ale the potential microbial fungicides,it may be widely applied.In this study,endophytic bacteria were isolated from soybcan cultivar Hefeng 25 that was a main soybean cultivar in Heilongjiang province,China.The results indicated that the density of endophytic bacteria varied in different tissues of the plant.It was 3.4×103CFU/g in roots,2.8×103CFU/g in leaves,2.9×102 CFU/g in stems and 1.4×102 CFU/g in seeds.The activity of 121strains against Fusarium oxysporum f.sp.soybean,caused soybean root rot,were assayed.25.6% of them showed antagonistic activity against F. oxysporum f. sp.soybean.One of them,strain TF28 isolated from soybean roots could inhibit the growth of many fungal pathogens.The inhibitory rates against F. oxysporum from different plant species were 80.2%-96.7%.Based on the morphological,physiological and biochemical characteristics as well as the sequence of 16S rRNA,strain TF28 was identified as Bacillus amyloliquefaciens.

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Application of Microorganisms in the Degradation of Polluted Chemicals in Aquatic Environments

Yan PENG ; Junpeng CAI

Microbiology.2008;35(5):809-814.

Every year, waters on earth receive large quantities of wastewater from industry, agriculture, fish and poultry raising, and municipal sewage treatment plants. Consequently, the aquatic environment on the earth is under a serious challenge from a very large quantity of pollutants such as antibiotics, insecticides, herbicides, hydrocarbons, etc., contained in the domestic wastewater, industrial and agricultural waste water and illegal effluents. In particular, with the development of intensive aquiculture and poultry, the effluent pollution has recently become more and more serious with more attentions. Furthermore more and more chemical pollutants discharged into aquatic environment have been detected with the advancement of analytical techniques. These chemicals can cause toxic effects on water habitats after discharged into aquatic environment. However, microorganisms have many key functions in pollution control. In this review, applications of microorganism in the degradation of chemicals in aquatic environments are reviewed. It was concluded that most applications of microorganisms degrading chemicals focused on aquaculture waters, whereas other aquatic systems (such as river, lake, sea, coastal waters) have been scarcely studied.

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Molecular Cloning and Biochemical Characterization of Protocatechuate 3, 4-dioxygenase in Burkholderia sp.NCIMB 10467

Sha LUO ; Junjie ZHANG ; Ningyi ZHOU

Microbiology.2008;35(5):712-719.

Strain NCIMB 10467, a lignin degrader, was reclassified as genus Burkholderia according to its 16S rDNA sequence. It seems that the metabolism of protocatechuate by this strain is diverse under the induction of various substrates. A 9505-bp DNA fragment extending from α conserved region of the gene, which encodes β subunit of orthocleavage protocatechuate 3, 4-dioxygenase(P34D; EC 1.13.11.3),was obtained by genome walking. Sequence analysis revealed two deduced open reading frames, pcaG and pcaH, encoding the α and β subunits of P34D respectively in this fragment. The P34D activity could be detected when pcaGH were expressed in E. Coli and the disruption of pcaH in strain NCIMB 10467 has lead to loss of its ability to catabolize protocatechuate. It was proved that the cloned pcaGH were encoding a functional protocatechuate 3, 4-dioxygenase which was necessary for the protocatechuate metabolism in this strain.

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Characterization of AcrA gene from Vibrio alginolyticus Strain HY9901

Shuanghu CAI ; Zaohe WU ; Jichang JIAN ; Yishan LU

Microbiology.2008;35(1):67-72.

A 460 bp internal fragment of the AcrA gene from Vibrio alginolyticus strain HY9901 was amplified by PCR with designed primers and the unknown flanking sequence of 5 '- and 3 '- ends of the AcrA gene was finally characterized by inverse PCR and nested PCR. Sequence analysis showed the AcrA gene contained 1101 bp ORF encoding 366 amino acids and the deduced amino acid sequence of the precursor from Vibrio alginolyticus strain HY9901 showed significant homology with the putative protein of other Vibrio species. The AcrA shows 76%, 73%, 71% and 70% homology with V.vulnificus strain YJ016, V. parahaemolyticus strain RIMD 2210633, V. splendidus strain 12B01 and V. cholerae O1 biovar eltor str. N16961 respectively.

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STUDY ON THE ASTAXANTHIN-PRODUCING YEAST PHAFFIA RHODOZYMA MUTATED BY NTG

Jiang WU ; Ziyi LIU ; Shoumin ZHU

Microbiology.2001;28(2):33-37.

astaxanthin is an effective antioxidant and natural pigment which has wide application. Phaffia rhodozyma is a good source of astaxantin, but wild strain has limited use in industry because of low production level of astaxanthin. Several mutants of Phaffia rhodozyma were obtained by exerting mutagen N-methyl-N-nitro-N-nitrosoguanidine. The growth curve suggested that pigments were mainly produced in the middle and latter periods of log phase. The pigments were extracted from Phaffia rhodozyma and analysed by esterification, thin layer chromatography and absorption spectrometry. It was proved that astaxanthin, astaxanthin diester and β-carotene were the major components of the pigments produced by Phaffia rhodozyma. We also studied the pigments producing phase of Phaffia rhodozyma. and founded that astaxanthin was stable to light under butylatedhydroxytoluene coexistance.

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THE EFFECT OF FERMENTATION ON CELLULOLYTIC ENZYME ACTIVITY

Jingmei PANG ; Lijun LI ; Jun GUO ; Gaimei LIANG ; Xiaoyan JIAO

Microbiology.2001;28(2):30-33.

Four cellulolytic strains, which can be used as feed additive, were studied under the conditions of various temperature, incubation time, and anaerobic process, and examined the changes of their cell protein content, cellulase and hemi-cellulase activity. The results show: 1) The maximum cellulolytic enzyme activities were observed incubation 20h; 2) Constant medium temperature 28℃ was adequate to the growth of the 4 strains ; 3) anaerobic condition, 39℃±2℃ and fermentation 12h, 24h, 36h, the tested strains can growth well in PDA plate, however, the cellulolytic enzyme activities and growth of the tested strains were influenced adversely when fermentation 48h. The experiment provide many important basis for the strains production, storage and utilization.

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CAPACITY OF SOME BACTERIA AND FUNGI IN DISSOLVING PHOSPHATE ROCK

Qimei LIN ; Hua WANG ; Xiaorong ZHAO ; Zijuang ZHAO

Microbiology.2001;28(2):26-30.

Four bacterial and 8 fungal isolates were incubated in media for 6 days. It was found that organic acid content in the media increased largely, but pH decreased sharply. Phosphorus content in the media enhanced dramatically as well. The fungal isolates showed stronger ability to dissolve phosphate rock than the bacterial ones. These isolates excreted not only quite distinct volume of organic acids but diverse organic acid chemicals. The fungi produced more kinds of organic acids than the bacteria. However, there was no significant relationship between the total quantity of organic acids and P content in the media.

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ISOLATION AND IDENTIFICATION OF ATRAZINE-DEGRADING STRAINS

Baoli CAI ; Jinyong HUANG ; Jiandang SHI ; Xinping ZHANG ; Hai LIU ; Changshou ZHU

Microbiology.2001;28(2):22-26.

Six atrazine-degrading strains, Pseudomonas spp. AD1, AD2, AD6, Agrobacterium sp. AD4, Xanthomonas AD5, and Erwinia sp. AD7, were isolated from industrial wastewater. These strains are able to grow on atrazine as sole nitrogen source. Strain AD1 is able to degrade atrazine of 0. 3g/L in minimal medium at a percentage of 99.9% in 72 hours. PCR products that are homologous to the atrazine chlorohydrolase gene atzA)from Pseudomonas sp. strain ADP were obtained by PCR method using total DNA of the strains AD1 ,AD4,AD5,AD6,and AD7 as templates.

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STUDY ON PHYSIOLOGICAL AND BIOCHEMICAL PROPERTIES OFα-ACETOLACTATE DECAROBOXYLASES FROM DIFFERENT MICROBES

Xiuping HE ; Wenhui HUAI ; Wenjie GUO ; Borun ZHANG

Microbiology.2001;28(2):18-21.

The enzyme activity of α－Acetolactate Decaroboxylases (ALDC)from different microbes was studied, the results demonstrated that it was quite different among them. There were diversities of their enzyme reaction velocities. It was clear that the enzyme activity was affected by the pH of the enzyme reaction system, for example, the optimum pH of ALDC from Lactococcus lactis was 6.6, while for Aerobacter Aerogenes it was 5.8. Addition leucine,valine and isoleucine into enzyme reaction system obviously affected the enzyme activity of ALDC from different microbes.

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