Characterization of beneficial properties of plant growth-promoting rhizobacteria isolated from sweet potato rhizosphere

Laboratory study was conducted to characterize the beneficial properties of plant growth-promoting rhizobacterial (PGPR) strains isolated from sweet potato rhizosphere. Fifteen rhizobacterial (PGPR) strains were screened for indole acetic acid (IAA) production with and without addition of the precursor L-tryptophan (L-TRP), phosphate-solubilizing activity, and nitrogen production, antagonistic activity against fungal pathogens, siderophore production and intrinsic antibiotic resistance. Results of the laboratory study showed that 15 rhizobacterial isolates were able to produce indole acetic acid (IAA). The concentration of IAA produced ranged from 3.84 - 13.33mg L-1. Addition of L-tryptophan (L-TRP) to the bacterial isolates increased the production of IAA ranging from 4.94 - 46.66 mg L-1. Six isolates (40%) were able to solubilize insoluble phosphate as evident by production of clear zone on calcium phosphate medium. All isolates were able to grow in N-free media indicating their abilities to produce nitrogen which ranged from 0.74 - 1.32 ppm. Three of the isolates produced fluorescent pigment on agar plate indicated their abilities to produce siderophores. Four isolates were able to inhibit the fungal pathogens Rhizoctonia sp.and Pythium sp. The intrinsic antibiotic test showed that all isolates were resistant against chloramphenicol (10 and 30 µg mL-1), Streptomycin (10 µg mL-1), Kanamycin (5 and 30 µg mL-1), Penicillin (10 µg mL-1) and tetracyclin (30 µg mL-1). The rhizobacterial isolates showed the several beneficial traits that could improve plant growth

Growth and storage root development of sweetpotato inoculated with rhizobacteria under glasshouse conditions

A pot experiment was conducted to determine the effects of rhizobacterial inoculation on growth and storage root development of Sepang Oren sweetpotato. Inoculation positively affected plant growth. The highest growth was observed on plants inoculated with Klebsiella sp. which increased shoot dry weight by 23% compared to control. Five of the isolates were able to produce sweetpotato storage roots. Klebsiella sp. and Erwinia sp. produced higher storage root yields of 35.15 and 8.22 g plant-1, respectively, compared to the other treatments. The inoculation significantly increased the uptake of nutrients in plant tissue and the concentrations of nutrients in soil. The results suggest that Klebsiella sp. and Erwinia sp. are potentially effective as bioenhancers and biofertilizers for sweetpotato

An Approximate Model of Load Frequency Control Systems with Time Delay

In this paper we present an approximate model for load frequency control system with time delay. The load frequency control is one of the conventional power system control problems. In order to secure the stability of the grid the frequency must remain within its limited range which is achieved through the load frequency control. The load frequency control signals experience time delay that could destabilize the power systems. The presence of the time delay complicates the analysis of the load frequency control system. In this paper we present a stability method based on the Direct Frequency Response approximation for the time delay. This approximation transforms the transcendental time delay equation into linear equation. This results in a simple stability criterion for the load frequency control system with time delay. A one-area load frequency control system is chosen as a case study. The effectiveness of the proposed approximation has been tested through simulation and comparison with the published research work. By tracking the eigenvalues or using Routh's criterion the maximum delay margin can be estimated. The proposed stability criterion has been compared with the most recent methods and showed it is merit. The range of the PI controller parameters for a given time delay can be determined which is very important in practice

Review of an Accurate System Utilizing GPS Technology

GPS provides precise position and control data anywhere on the planet and in any weather condition. GPS was originally intended for military usage, but in the 1980s, the US Department of Defense made it available for civilian use. The scientific applications of GPS in the military, community, and commercial sectors are expanding on a regular basis. Agriculture, construction, mining, measurement, package delivery, and logistical supply chain management all benefit from GPS technology. Precision GPS time synchronization is critical for big networks, navigation, finance systems, financial markets, and power grids. Wireless services are impossible to imagine without them. In this paper, we will go over the key aspects of GPS technology as well as a discussion of the systems that use it

An overview of hepatitis B virus surface antigen mutant in the Asia Pacific

Hepatitis B virus infection is a serious health problem worldwide, and more than 350 million people are chronic carriers, constituting a major global threat. Southeast Asia and the Western Pacific have the highest levels of endemicity in the world, with an estimated seroprevalence ranging between 2% and 31%. Mutations in the hepatitis B surface antigen (HBsAg) have been reported in many parts of the world but are most common in Asian infants; such mutants have several clinical effects, such as the development of hepatocellular carcinoma. Diagnostic failures by commercial assays have reduced the diagnostic effectiveness of HBsAg detection. For example the substitution of an amino acid in the major hydrophilic region of the S gene reduces the binding of hepatitis B surface antibodies leading to immune escape. The safety of blood transfusion may be compromised by current screening tests due to escape from being neutralised by antibodies induced by HBsAg mutants, and undetectable levels of viral surface protein. Data on the epidemiology of HBsAg mutation in Asia Pacific are scant; however, this manuscript has reviewed the available information on the epidemiology of HBsAg mutation in Asia Pacific

Occult hepatitis B infection among vaccinated cohort

BACKGROUND: Occult hepatitis B is characterized by undetectable levels of surface antigen, but detectable levels of viral DNA and is becoming a major global threat due to: (i) the effect on the health of children born to carrier mothers despite the presence of passive immunoglobulin at birth (ii) immune escape of current vaccines; and (iii) spread through blood and blood products in post transfusion infection, organ donation, and sexual transmission. The aim of this study is to investigate occult hepatitis B virus among vaccines. METHOD: Four hundred and eight, vaccinee were recruited for this study. All samples were tested for hepatitis B surface antigen, hepatitis B surface and core antibodies using enzyme-linked immunosorbent assay kit (DRG International Inc., USA). Positive samples were re-tested to exclude false positive results. Molecular technique using a nested polymerase chain reaction was done using primers specific to the surface gene. RESULTS: Persistence of hepatitis B surface antibodies (≥10 IU/L) was found in 62.5% (255/408) with 37.5% (153/408) having anti-HBs<10 IU/L in circulation. Hepatitis B core antibodies among vaccinated cohort were found to be 5.0% (20/408). Of which 80% (16/20) of the hepatitis B core antibodies positive, have positive hepatitis B surface antibodies (≥10 IU/L) while 20% (4/20) are negative (<10 IU/L). The former is indicating immunity as a result of previous infection and the latter group are referred to as isolated anti-core, as described in previous studies (1). However none of the samples is hepatitis B surface antigen positive. Hepatitis B viral DNA was detected in all the core antigen positive individuals, contrary to studies in Turkey and Taiwan and in line with other similar studies(2). Occult hepatitis B infections have significant clinical importance since they can become reactivated when the immune system is suppressed and can be transmitted through blood or blood product transfusion, organs transplant, and sexual intercourse. CONCLUSION: The result of this study shows occult chronic HBV infection among adults who were vaccinated against hepatitis B vaccine at infant. The anti-HBs produced were induced by the vaccine they received but do not provide protection against the mutant’s variant suggesting primary infection with mutant’s hepatitis B virus

Hot water extract of Chlorella vulgaris induced DNA damage and apoptosis

OBJECTIVES: The aim of this study was to determine the antiproliferative and apoptotic effects of hot water extracts of Chlorella vulgaris on hepatoma cell line HepG2. INTRODUCTION: The search for food and spices that can induce apoptosis in cancer cells has been a major study interest in the last decade. Chlorella vulgaris, a unicellular green algae, has been reported to have antioxidant and anti-cancer properties. However, its chemopreventive effects in inhibiting the growth of cancer cells have not been studied in great detail. METHODS: HepG2 liver cancer cells and WRL68 normal liver cells were treated with various concentrations (0-4 mg/ml) of hot water extract of C. vulgaris after 24 hours incubation. Apoptosis rate was evaluated by TUNEL assay while DNA damage was assessed by Comet assay. Apoptosis proteins were evaluated by Western blot analysis. RESULTS: Chlorella vulgaris decreased the number of viable HepG2 cells in a dose dependent manner (p < 0.05), with an IC50 of 1.6 mg/ml. DNA damage as measured by Comet assay was increased in HepG2 cells at all concentrations of Chlorella vulgaris tested. Evaluation of apoptosis by TUNEL assay showed that Chlorella vulgaris induced a higher apoptotic rate (70%) in HepG2 cells compared to normal liver cells, WRL68 (15%). Western blot analysis showed increased expression of pro-apoptotic proteins P53, Bax and caspase-3 in the HepG2 cells compared to normal liver cells WRL68, and decreased expression of the anti-apoptotic protein Bcl-2. CONCLUSIONS: Chlorella vulgaris may have anti-cancer effects by inducing apoptosis signaling cascades via an increased expression of P53, Bax and caspase-3 proteins and through a reduction of Bcl-2 protein, which subsequently lead to increased DNA damage and apoptosis

Colitis pseudomembranosa: entre la confirmación y la sospecha: una única decisión

La colitis pseudomembranosa es una entidad que se caracteriza fundamentalmente por una diarrea acuosa aunque sus manifestaciones pueden variar desde un paciente totalmente asintomático hasta una enfermedad fulminante con megacolon tóxico. Su evolución es variable y constituye un verdadero problema sanitario, en particular en la población anciana donde presenta una elevada morbilidad y mortalidad.Facultad de Ciencias Médica