Gluconic acid production by bacteria to liberate phosphorus from insoluble phosphate complexes

Ten indigenous bacterial isolates were identified as efficient mineral phosphate solubilisers namely 7 strains of Klebsiella pneumoniae, 2 strains of Enterobacter aerogenes and 1 strain of Pseudomonas aeruginosa. All the ten strains were able to dissolve calcium phosphate (Ca-P), ferric phosphate (Fe-P) and aluminium phosphate (Al-P) efficiently. STMPSB 8 (Klebsiella pneumoniae) could be designated as the best mineral P solubiliser for all the three insoluble mineral phosphates as it exhibited high solubilisation capacity for Ca-P, Fe-P and Al-P whereas STMPSB 6 (Enterobacter aerogenes), STMPSB 4 (Enterobacter aerogenes) and STMPSB 8 (Klebsiella pneumonia) were regarded as good gluconic acid producing bacteria. A strong correlation of 0.795, significant at the level of 0.01 was observed between gluconic acid concentration and calcium phosphate solubilisation. The detection of pyrroloquinoline quinone (pqq C) gene in eight of the bacterial isolates indicates that direct oxidation pathway was used during the biosynthesis of gluconic acid with the aid of pyrroloquinoline quinone cofactor

Green bean (Vigna radiata) seedling growth inhibition by Chromobacterium violaceum under in-vitro condition.

Chromobacterium violaceum is a pathogenic soil bacterium producing violacein and hydrogen cyanide both of which is controlled by quorum sensing with the same signal molecule homoserine lactone (C6-HSL). A study was carried out to determine if quorum sensing was a factor that was required for inhibiting the growth of green bean ( Vigna radiata) seedling. The results showed that C. violaceum which reached quorum level inhibited the growth of green bean seedling as much as 86.5% for the shoot length and 92.1% for the root length. However inhibition was reduced to 37.5% for the shoot and 17.5% for root if the quorum level of C. violaceum was not reached under an aseptic environment. Furthermore sterilised inoculant (killed) which had not reached quorum level would not affect the growth of green bean seedlings. These results indicate that quorum sensing in C. violaceum is a factor that determines its inhibitory effect on seedling growth

Biochemical diversity of bacterial isolates from paddy soils of peninsular Malaysia

In this study, the diversity of bacterial isolates from paddy soil located in several rice growing areas of Peninsular Malaysia was evaluated. Phenotypic and physiological characteristics of the isolates were recorded to categorize and identify the bacteria. Ten strains of bacteria were recovered from six different locations (Alor Bakat, Kg. Seligi, Bachok, Kelantan; Sekinchan, Selangor; Kobah, Kedah; and Sg. Batu Pahat, Perlis). The spread-plate technique on nutrient agar at pH 7.0 was used to isolate and purify all the strains. The characteristic of the bacteria strains were determined using the Gram staining, motility test, as well as the shape and size of the single colony on solid media. From the various tests conducted, nine isolates were identified as Gram-positive rods, and only one was Gram-negative cocci. Further biochemical tests were carried out to determine the ability of these bacteria strains to hydrolyze starch, casein and gelatine, ferment carbohydrate (glucose, lactose and sucrose), enzyme production (catalase and oxidase), MR-VP tests and growth under anaerobic condition; the elevated NaCl was also examined. On the basis of these tests and the biochemical characteristics, nine of the strains belonged to the same genus, Bacillus, with three potentially different species. Meanwhile, only one strain showed the characteristics related to Proteus mirabilis. This study also showed that the dominant bacteria genera are generally limited, despite the contrasting geographical location and soil characteristics in which the strains were isolated

Effect of Partial Rootzone Drying (PRD) on growth, Water Use Efficiency (WUE) and yield of tomatoes grown in soilless culture

An investigation was carried out at the Department of Crop Science, Universiti Putra Malaysia (UPM) to examine the effect of PRD using soilless media, a mixture of 70% coconut coir dust and peat (3:2 respectively) amended with 30% rice straw compost. Tomato (Lycopersicon esculentum Mill cv Red Rock) plants were exposed to two different water treatments, which was either well-watered (control) or partially irrigated on half of the roots (PRD). Reduction in water availability in the media with PRD treatment caused a significant decrease in leaf expansion, leaf area and stomatal conductance. Proline was significantly increase with PRD. There was no significant reduction in dry matter partitioning and yield between well-watered and PRD-treated plants. Water use efficiency also was significantly increased with PRD

Repeated fed-batch cultivation of nitrogen-fixing bacterium, Bacillus sphaericus UPMB10, using glycerol as the carbon source

The exponential fed-batch cultivation of Bacillus sphaericus UPMB10 in 2 l stirred tank fermenter was performed by feeding the initial batch culture with 14 g l-1 of glycerol according to the algorithm aimed at controlling the specific growth rate (µ) of the bacterium. Very high viable cell count (1.14 x 1010 cfu ml-1), which was four times higher as compared to batch cultivation, was achieved in the fed-batch with a controlled µ at 0.4 h-1. In repeated exponential fed-batch cultivation, consisting of four cycles of harvesting and recharging, a final cell concentration of 1.9 x 1011 cfu ml-1 was obtained at the end of the fourth cycle (46 h). Meanwhile, acetylene reduction of cell samples collected from repeated fed-batch cultivation remained unchanged and was maintained at around 20 nmol C2H2 h-1 ml-1 after prolonged cultivation period, and was comparable to those obtained in batch and exponential fed-batch cultivation. Glycerol could be used as a carbon source for high performance cultivation of B. Sphaericus, a nitrogen fixing bacterium, in repeated fed-batch cultivation with high cell yield and cell productivity. The productivity (0.68 g l-1 h-1) for repeated fed-batch cultivation increased about 6 times compared to that obtained in conventional batch cultivation (0.11 g l1 h-1). A innovative method in utilizing glycerol for efficient cultivation of nitrogen fixing bacterium could be beneficial to get more understanding and reference in manipulating the integrated plans for sustainable and profitable biodiesel industry

A review on microbial mutagenesis through gamma irradiation for agricultural applications

Gamma irradiation is widely used in sterilization and mutagenesis, especially for plant breeding and crop protection. Microbial mutagenesis through gamma irradiation is mainly applied in fermentation industry. In agriculture, gamma irradiation is mostly applied in crop improvement. Microbial mutagenesis is mainly applied against fungus and spore-forming bacteria, which are resistant to gamma irradiation. Response of microbes to gamma irradiation varies and depends on various factors. Review of previous works on gamma irradiation for microbial mutagenesis in agriculture may provide some information for the use of this method. The general view on gamma irradiation, its application, and mutagenesis are discussed in this paper. Further investigation on microbial mutagenesis should consider molecular changes, information on which is lacking in previous works. Moreover, studies on microbial mutagenesis are still lacking in Malaysia despite having several gamma irradiation facilities. Therefore, further studies on microbial mutagenesis should be conducted

Development of compatible lignocellulolytic fungal consortium for rapid composting of rice straw.

An experiment was conducted to evaluate the potential of lignocellulolytic fungi for rapid composting of rice straw. Forty-nine isolates of fungi were isolated from several natural and induced rice straw composting sources. Ten isolates were tested for their potential to decompose lignocellulosic rice straw by assessing their growth rate and biomass production, as well as their ability to decompose lignin and cellulose on rice-straw-powder-amended media. Four isolates (F26, F28, F29, and F44) were selected as potential lignocellulolytic agents for in-vitro compatibility study based on their optimum growth rate, biomass production, and lignocellulolytic activities. Six different interactions were found among four interacting isolates in the form of mutual intermingling, partial mutual intermingling, and inhibition at the contact point. Finally, a consortium of Aspergillus niger (F44) and Trichoderma viride (F26) was tested for in-vitro biodegradation of rice straw. The fungal consortium was able to decompose cellulose, hemicelluloses, lignin, and total carbon significantly (p ≤ 0.05) over the control. The C/N ratio was reduced to 19.5 from an initial value of 29.3 in three weeks of the biodegradation process, thus showing the potential of this method for use in large-scale composting of rice straw