Aggressiveness of Ganoderma boninense and G. zonatum isolated from upper- and basal stem rot of oil palm (Elaeis guineensis) in Malaysia

By: Rakib, M.R.M.; Bong, C.F.J.; Khairulmazmi, A. and Idris, A.S.

Journal of Oil Palm Research --- Year 2015; Volume 27; Issue 3; Page 229-240

Keywords: basal stem rot, Ganoderma boninense, Ganoderma zonatum, pathogenicity, upper stem rot

Abstract

Cur­rently, the most known dev­as­tat­ing oil palm dis­ease through­out South-east Asia is basal stem rot (BSR) caused by Gan­o­derma boni­nense. How­ever, there is insuf­fi­cient infor­ma­tion on G. zona­tum which also has been asso­ci­ated with the BSR, and upper stem rot (USR). Thus, this study reports patho­log­i­cal symp­toms and degree of aggres­sive­ness amongst G. zona­tum and G. boni­nense of USR and BSR on oil palm seedlings. All the Gan­o­derma iso­lates tested showed pos­i­tive signs of infec­tion on the seedlings at 12 and up to 24 weeks after inoc­u­la­tion. How­ever, the symp­toms of infec­tion on the seedlings were indis­tin­guish­able amongst the Gan­o­derma species tested. In fact, they showed sig­nif­i­cantly dif­fer­ent degree of aggres­sive­ness in terms of area under dis­ease progress curve (AUDPC), epi­demic rate, sever­ity of foliar symp­toms (SFS), dis­ease sever­ity index (DSI), stem bole necro­sis and pri­mary roots necro­sis. The present find­ings sug­gested that G. zona­tum of USR was the most aggres­sive, fol­lowed by G. zona­tum and G. boni­nense of BSR, and G. boni­nense of USR was the least aggres­sive. Hence, a new mech­a­nism of con­trol strate­gies is urgently required to con­tain the dis­ease from spread­ing espe­cially for USR and also for G. zona­tum in Malaysia.

Influence of long-term fertilization on soil microbial biomass, dehydrogenase activity, and bacterial and fungal community structure in a brown soil of northeast China

By: Peiyu Luo; Xiaori Han; Yan Wang; Mei Han; Hui Shi; Ning Liu and Hongzhi Bai

Annals of Microbiology --- Year 2015; Volume 65; Issue 1; Page 533-542

Keywords: Long-term fertilization; Bacterial and fungal community structure; Soil microbial biomass carbon; Dehydrogenase activity; PCR-DGGE

Abstract

In this study, the effect of mineral fertilizer and organic manure were evaluated on soil microbial biomass, dehydrogenase activity, bacterial and fungal community structure in a long-term (33 years) field experiment. Except for the mineral nitrogen fertilizer (N) treatment, long-term fertilization greatly increased soil microbial biomass carbon (SMBC) and dehydrogenase activity. Organic manure had a significantly greater impact on SMBC and dehydrogenase activity, compared with mineral fertilizers. Bacterial and fungal community structure was analyzed by polymerase chain reaction (PCR)-denaturing gradient gel electrophoresis (DGGE). Long-term fertilization increased bacterial and fungal ribotype diversity. Total soil nitrogen (TN) and phosphorus (TP), soil organic carbon (SOC) and available phosphorus (AP) had a similar level of influence on bacterial ribotypes while TN, SOC and AP had a larger influence than alkali-hydrolyzable nitrogen (AHN) on fungal ribotypes. Our results suggested that long-term P-deficiency fertilization can significantly decrease soil microbial biomass, dehydrogenase activity and bacterial diversity. N-fertilizer and SOC have an important influence on bacterial and fungal communities.

Characterization of microbial communities in heavy crude oil from Saudi Arabia

By: Majed Albokari; Ibrahim Mashhour; Mohammed Alshehri; Chris Boothman and Mousa Al-Enezi
Annals of Microbiology --- Year 2015; Volume 65; Issue 1; Page95-104

Keywords: Heavy crude oil; Oil sludge; 16S rRNA; PCR amplification; Saudi Aramco oil company

Abstract
The complete mineralization of crude oil into carbon dioxide, water, inorganic compounds and cellular constituents can be carried out as part of a bioremediation strategy. This involves the transformation of complex organic contaminants into simpler organic compounds by microbial communities, mainly bacteria. A crude oil sample and an oil sludge sample were obtained from Saudi ARAMCO Oil Company and investigated to identify the microbial communities present using PCR-based culture-independent techniques. In total, analysis of 177 clones yielded 30 distinct bacterial sequences. Clone library analysis of the oil sample was found to contain Bacillus, Clostridia and Gammaproteobacteria species while the sludge sample revealed the presence of members of the Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, Clostridia, Spingobacteria and Flavobacteria. The dominant bacterial class identified in oil and sludge samples was found to be Bacilli and Flavobacteria, respectively. Phylogenetic analysis showed that the dominant bacterium in the oil sample has the closest sequence identity to Enterococcus aquimarinus and the dominant bacterium in the sludge sample is most closely related to the uncultured Bacteroidetes bacterium designated AH.KK.

Soil chemical properties affect the reaction of forest soil bacteria to drought and rewetting stress

By: Marcin Chodak; Marcin Gołębiewski; Justyna Morawska-Płoskonka; Katarzyna Kuduk and Maria Niklińska
Annals of Microbiology --- Year 2015; Volume 65; Issue 3; Page 1627-1637

Keywords: Drought and rewetting stress; Forest soils; Bacterial phyla; Soil chemical properties; Pyrosequencing

Abstract
Reaction of soil bacteria to drought and rewetting stress may depend on soil chemical properties. The objectives of this study were to test the reaction of different bacterial phyla to drought and rewetting stress and to assess the influence of different soil chemical properties on the reaction of soil bacteria to this kind of stress. The soil samples were taken at ten forest sites and measured for pH and the contents of organic C (Corg) and total N (Nt), Zn, Cu, and Pb. The samples were kept without water addition at 20 – 30 °C for 8 weeks and subsequently rewetted to achieve moisture equal to 50 – 60 % of their maximum water-holding capacity. Prior to the drought period and 24 h after the rewetting, the structure of soil bacterial communities was determined using pyrosequencing of 16S rRNA genes. The drought and rewetting stress altered bacterial community structure. Gram-positive bacterial phyla, Actinobacteria and Firmicutes, increased in relative proportion after the stress, whereas the Gram-negative bacteria in most cases decreased. The largest decrease in relative abundance was for Gammaproteobacteria and Bacteroidetes. For several phyla the reaction to drought and rewetting stress depended on the chemical properties of soils. Soil pH was the most important soil property influencing the reaction of a number of soil bacterial groups (including all classes of Proteobacteria, Bacteroidetes, Acidobacteria, and others) to drought and rewetting stress. For several bacterial phyla the reaction to the stress depended also on the contents of Nt and Corg in soil. The effect of heavy metal pollution was also noticeable, although weaker compared to other chemical soil properties. We conclude that soil chemical properties should be considered when assessing the effect of stressing factors on soil bacterial communities.