Yeast Extract Mannitol Research Articles

Cultural and Biochemical Characteristics of Rhizobium Present in Nodule of Pongamia Pinnata (l.) Pierre

The present investigation is an attempt to study the impact of rocky terrain on Rhizobium bacteria of root nodules isolated from legume trees. To study the morphological, cultural, and biochemical characteristics of bacterial strain the bacteria obtained from nodules of selected legume i.e. Pongamia pinnata. Rhizobia inhabited in root nodules of plant, grown in Kota university campus, rhizobia were isolated and inoculated on Yeast Extract Mannitol Agar (YEMA) medium and it’s morphological, cultural and biochemical characteristics were studied. It was observed that colonies were circular or irregular; light creamish, glistering, gelatinous, convex with entire margins. The bacteria were gram negative, rod shaped, aerobic, non-spore forming and slow-moving bacteria arranged single, in pairs and in clusters. It showed negative chemical reaction for indole, while showed positive reaction for citrate utilization, catalase, urease. By the help of bio chemical characteristics it was confirmed that isolated bacterial culture may be of Rhizobium pongamie and rocky terrain with high temperature of environment does not have any negative effect on the characters of Rhizobium, our findings was supported by many earlier investigations.

Assessing The Toxicity Of Heavy Metals And Potential Tolerance Of Common Bean (Phaseolus vulgaris) While Monitoring The Population Dynamics Of The Associated Rhizobia

Microbially-assisted phytoremediation (MAP) is increasingly recognized as the feasible alternative for removing hazardous heavy metals (HMs) from contaminated environments. However, the dynamics of rhizobial-plant interactions during phytoremediation remain unclear. This study investigated the toxicity of some selected heavy metals (Cobalt, Nickel, and Manganese), the potential tolerance of Phaseolus vulgaris grown in the HMs-rich effluents, and the population dynamics of the associated Rhizobia within the Katsina metropolis. After 80 samples of P. vulgaris collected from Lambun Sarki garden were exposed to 10 mL of 0.5-2g/L of Ni and Co and 5-20 g/L Mn, respectively, in mesocosms, and the plants treated with 10 mL HMs solutions daily, for three weeks. Indices of HMs toxicity on seeds and plants (4 and 3, respectively) were monitored in all treatments. Weekly rhizobial counts on Congo Red Yeast Extract Mannitol Agar (CRYEMA) were taken to monitor rhizobial population dynamics. Pure isolates obtained after three iterations were identified biochemically. One-way ANOVA was employed for statistical analyses using AnalyStat (version 1.6.50). Generally, Ni exerts the highest toxicity, with Mn having less toxicity. Average rhizobial counts increased weekly, with high counts obtained in Ni and Mn treatments. However, they did not differ significantly between weeks (p = 0.061). Thus, longer time intervals (>2 weeks) are required to observe significant shifts in population dynamics. Moreover, HMs concentration did not affect the colony counts (p = 1.00). Metabolism profile of the preliminarily identified Rhizobium sp. and Sinorrhizobium melliloti evidenced HMs removal and plant growth promotion ability. The research demonstrated the phytoremediation ability of P. vulgaris and how rhizospheric population dynamics change during phytoremediation and contributed towards understanding HMs impact as environmental stressors on rhizospheric plant-microbe interactions. Future research targeting the hyperaccumulation capacity of the plants and heavy metals tolerance of the identified rhizobia are recommended, as this may help in knowing the BCF, TF, and BAC of the plants as well as the tolerable amount of the heavy metals to the bacteria

Comparing the population density, colony diversity, and phosphate solubilization ability between rice root endophytic and rice rhizospheric soil bacteria from organic wetland

Abstract Phosphate-solubilizing bacteria (PSB) play important roles in the agricultural systems. The present study aims to compare the population density, colony diversity, and phosphate solubilization ability between rice root endophytic bacteria (RRoEB) and rice rhizospheric soil bacteria (RRzSB) from organic wetland. By spread plate method, bacteria were isolated directly using Pikovskaya’s agar and indirectly through other media, namely Nutrient Agar (NA), Starch Casein Agar (SCA), Jensen, and Yeast Extract Mannitol Agar (YEMA). Each distinct colony based on the morphology on the respective media was screened for phosphate solubilization ability by subculturing on Pikovskaya’s agar. The phosphate solubilizing index (PSI) was measured from the halo zone formation. The results showed that by direct isolation, 6 RRoEB and 5 RRzSB were able to phosphate solubilization. By indirect isolation from NA, SCA, Jensen, and YEMA, 2, 3, 1, and 3 isolates of RRoEB and 4, 3, 1, and 3 isolates of RRzSB showed the capability as phosphate solubilizer. Although the highest colony diversity of PSB was obtained from direct isolation, however the highest PSI was yielded from indirect isolation, namely isolates J1R1 (3.53) and Y1S1 (2.48). The highest PSI from direct isolation was obtained by P1R5 (1.90) and P1S1 (1.51).

Production of Exopolysaccharides and İndole Acetic Acid (IAA) by Rhizobacteria and Their Potential against Drought Stress in Upland Rice.

Peatlands are marginal agricultural lands due to highly acidic soil conditions and poor drainage systems. Drought stress is a big problem in peatlands as it can affect plants through poor root development, so technological innovations are needed to increase the productivity and sustainability of upland rice on peatlands. Rhizobacteria can overcome the effects of drought stress by altering root morphology, regulating stress-responsive genes, and producing exopolysaccharides and indole acetic acid (IAA). This study aimed to determine the ability of rhizobacteria in upland rice to produce exopolysaccharides and IAA, identify potential isolates using molecular markers, and prove the effect of rhizobacteria on viability and vigor index in upland rice. Rhizobacterial isolates were grown on yeast extract mannitol broth (YEMB) medium for exopolysaccharides production testing and Nutrient Broth (NB)+L-tryptophan medium for IAA production testing. The selected isolates identify using sequence 16S rRNA. The variables observed in testing the effect of rhizobacteria were germination ability, vigour index, and growth uniformity. EPS-1 isolate is the best production of exopolysaccharides (41.6 mg/ml) and IAA (60.83 ppm). The isolate EPS-1 was identified as Klebsiella variicola using 16S rRNA sequencing and phylogenetic analysis. The isolate EPS-1 can increase the viability and vigor of upland rice seeds. K. variicola is more adaptive and has several functional properties that can be developed as a potential bioagent or biofertilizer to improve soil nutrition, moisture and enhance plant growth. The use of rhizobacteria can reduce dependence on the use of synthetic materials with sustainable agriculture.

Influence of native rhizobacteria co‐inoculation and formulation of bacterial inoculants on the growth and yield of common bean (Phaseolus vulgaris L.)

AbstractIntroductionIncorporation of inoculum in different carrier materials may increase the efficacy of bacterial inocula.Materials and MethodsField experiments were conducted using two strains of rhizobium and phosphate‐solubilizing bacteria (PSB) and their respective combinations using different carrier materials in common bean‐growing regions in three soil types in Kenya. The field experiment was laid out in a split‐plot arrangement with the strain inoculations as the main plot while the subplots consisted of the carrier materials (filter mud, peat moss and yeast extract mannitol broth [YEMB]). Each main plot included two controls: uninoculated negative control and uninoculated controls that received N and P fertilizer. The experiment was conducted for two cropping seasons. Data were collected on the nodulation, shoot and root biomass and yield.ResultsCo‐inoculation of the common bean with Rhizobium phaseoli + Bacillus aryabhattai strains had significantly higher number of nodules (55 nodules per plant) compared to single R. phaseoli inoculation (38 nodules). The co‐inoculation of the rhizobia and the PSB yielded statistically at par with the application of diammonium phosphate (18:46:0) across the soil types and seasons. The use of filter mud as a carrier material led to a higher number of nodules for most of the rhizobia strains inoculation and their respective co‐inoculation with the bacillus strains. Significantly higher yield was obtained with the filter mud (1.64 Mg ha−1) while there was no significant difference in the yield of common bean between peat moss and YEMB as carrier materials for the bacterial strains.ConclusionThe solid carrier material, specifically filter mud, showed potential for use in the formulation of inoculants. Specific co‐inoculation of rhizobia (R. phaseoli and Rhizobium pusense strains) and PSB (Paenibacillus polymyxa and B. aryabhattai) increased the growth, nodulation and yield of common bean more efficiently than the control.

Ecotoxic response of Rhizobium sp. to the commonly used pesticides (paraquat and dichlorvos)

This study investigated the 96-hour ecotoxicity response of Rhizobium sp. to paraquat and dichlorvos at application concentrations ranging from 0.01 mg/L to 100 mg/L. The test organism was isolated and enumerated using yeast extract mannitol agar. Paraquat proved to be more toxic than dichlorvos based on the toxicity parameters established using probit regression analysis. Rhizobium sp. showed no growth (100% mortality) at the higher concentrations of 10 mg/L and 100 mg/L for paraquat; for dichlorvos, this absence of growth was only seen at the highest application concentration of 100 mg/L. Overall, Rhizobium sp. tolerated the insecticide, dichlorvos, better than the herbicide, paraquat. At the lowest concentration of 0.01 mg/L, it displayed moderate tolerance indices of between 0.534 and 0.589 for both pesticides. At 0.1 mg/L and 1.0 mg/L pesticide concentrations, the 96-hour tolerance indices obtained were less than 0.39, indicative of very low tolerance. Neither pesticide was tolerated at 10 mg/L and 100 mg/L. Statistical comparisons of the tolerance indices between the two pesticides and from one pesticide concentration to the other showed significant differences both within and the between groups (p≤0.05). The median lethal concentrations (LC50) were 0.0158 mg/L and 0.0350 mg/L for paraquat and dichlorvos, respectively. The lowest observed effect concentration (LOEC) and no observed effect concentration (NOEC) were 0.0011 and 0.0027, respectively for paraquat and 0.0017 and 0.0047, respectively for dichlorvos. The results indicated that pesticides have adverse acute effects on key microbial ecosystem service providers like Rhizobium sp. and should, thus, be used with restraint.

Effect of glyphosate on the growth and survival of rhizobia isolated from root nodules of grass pea (Lathyrus sativus L.)

Grass pea (L. sativus L.) is a widely cultivated crop worldwide, forming a symbiotic relationship with nitrogen-fixing rhizobia. Glyphosate is commonly used by farmers for weed control during agricultural processes. However, the application of this chemical herbicide negatively impacts soil fertility by affecting the nitrogen-fixing rhizobia. This study aimed to assess the effects of glyphosate on rhizobia isolated from healthy and robust Grass pea plants. Specifically, Grass pea plants exhibiting vigorous growth and a healthy appearance were intentionally selected to isolate rhizobia from their root nodules. The isolated rhizobia were then characterized based on their morphological features, biochemical properties, and resistance to abiotic traits. Rhizobial isolates from grass peas exhibited Gram-negative, rod-shaped morphology, milky colony color, and variable colony sizes. Additionally, the majority displayed smooth colony surfaces on yeast extract mannitol agar medium. Based on morphological and biochemical characteristics, the isolates could be grouped under the genus Rhizobium. Optimum growth conditions for these isolates were observed at temperatures between 28 and 38 °C, pH levels ranging from 5 to 8, and salt (NaCl) concentrations of 0.5% and 1%. At a concentration of 20 mL L−1, glyphosate inhibited 5.52–47% of the Rhizobium population. The inhibition percentage increased to 17.1–53.38% at a concentration of 40 mL L−1. However, when exposed to a higher concentration (60 mL/L) of glyphosate, 87% of the isolates were inhibited. The number of colonies after glyphosate exposure was significantly dependent on concentration, and there were notable differences between treatments with varying glyphosate concentrations (p < 0.05). Glyphosate negatively impacted the survival of grass pea rhizobia, leading to a reduction in the Rhizobium population (CFU). However, the effect varied between Rhizobium isolated from grass pea root nodules.

Effect of Chemical Mutagenesis on Salt Tolerance of Common Beans (Phaseolus vulgaris L.) Nodulating Rhizobium

The chemical mutation is one of the important factors in the enrichment of the salt resistance capacity of the rhizobium isolates. Therefore, this study focused on 10 isolates of rhizobium collected from soil samples of Babile, Hararghe region, Ethiopia. All the collected isolates turned into a moderately yellow, yellow, and deep yellow color in yeast extract mannitol agar medium (YEMA) containing bromothymol blue after 48 h of incubation. It indicated that all the isolates were acid-producing Rhizobia. Moreover, based on colony morphology and diameter, 70% of the isolates displayed large mucoid colonies, and 30% of the isolates showed large watery colonies in YEMA media. Among the 10 isolates, 9(90%), 9(90%), 6(60%), 6(60%), 2(20%), and 1(10%), were grown at different salinity levels such as 2%, 4%, 6%, 8%, 9% and 10% of NaCl, correspondingly. The most salt-resistant wild isolate was HUCR 6 collected from Babile soil grown at 10% NaCl salinity level. A total of six mutants were considered after chemical mutagenesis based on their capacity to survive in the extreme salinity levels (11 to 14%). Mutant isolates such as HUCRM 4, HUCRM 5, and HUCRM 6 were the most tolerant Rhizobium that grew at the salinity level of 11 to 14% NaCl. The most sensitive mutant isolate was HUCRM 10 followed by the isolates HUCRM 8 and HUCRM 9 was the next sensitive mutant Rhizobia that grew only at 11% of NaCl concentration. Compared to the Rhizobium wild isolates, the mutant isolates were observed to be more tolerant to a medium containing higher concentration of NaCl, as high as 11% to 14%. Besides, 80% of the mutant isolates demonstrated effective nodulation with the common beans. The mutant isolate (HUCRM 4) showed better performance in relation to root nodule performance of Rhizobium species and increased the plant biomass production. In this study, mutant isolates HUCRM 6, which is tolerated to 14% NaCl, and HUCRM 4, HUCRM 5, and HUCRM 6 isolates tolerated at 12% salinity level. Finally, based on their symbiotic efficiency and tolerance to extreme salt levels, these mutant isolates (HUCRM 4, HUCRM 5 and HUCRM 6) were encouraged to be used for the development of Rhizobium inoculants of common beans grown under extreme saline conditions. J. Bio-Sci. 30(2): 13-22, 2022

Genetic characterization and diversity analysis of heavy metal-resistant rhizobacterial strains isolated from the root nodules of Vigna trilobata determined by the R.A.P.D. technique

The present study characterizes twenty-one rhizobacterial strains isolated from root nodules of Vigna trilobata cultivars collected from various Andhra Pradesh, India districts. Rhizobacteria was isolated using selective medium Yeast Extract Mannitol Agar medium (Y.E.M.A.). All 21 strains were characterized based on colony morphology and biochemical characterization and identified up to species level by 16S rDNA sequencing analysis. Different genera of the bacteria are present in the root nodules of Vigna trilobata. Short random sequence primers amplify genomic D.N.A. in a process called random amplified polymorphic D.N.A. (R.A.P.D.), which were employed to assess genetic variation across isolated bacterial strains. Banding patterns were obtained via R.A.P.D. analysis of genomic D.N.A. from the isolates using five random primers, including OPA-4, OPA-9, OPA-11, OPA-12, and OPA-15. The R.A.P.D. profiles of twenty-one rhizobacterial isolates were compared separately to determine their differences by the occurrence of polymorphic D.N.A. fragments. PCR amplified of the D.N.A. isolated from twenty-one bacterial isolates yielded seventy amplified products, of which sixty-eight were polymorphic, and two were monomorphic. The investigation found that R.A.P.D. could differentiate between the strains very precisely. Characterizing and creating novel Rhizobium species can be aided by using molecular markers to investigate genetic diversity.

Isolation and Characterization of Nitrogen Fixing Bacteria from Rhizospher of Chickpea and Peanodules, Hossana, Ethiopia

One of the ways to increase the competitive survivability of rhizobial bio fertilizers and achieve better plant growth under such conditions is by modifying the rhizospheric environment or community by addition of non rhizobial nodule-associated bacteria (NAB) that cause better nodulation and plant growth when co-inoculated with rhizobia. To achieve this objective experimental design was carried out. Rhizobium is the root of legumes host nitrogen fixing bacteria which can invade root and get sugars from the plant. A study was performed to investigate the most commonly associated nodule-associated bacteria and the rhizospheric microorganisms associated with the legume plant. Present study on Isolation and characterization of Nitrogen Fixing Bacteria from agricultural rhizosphere was carried out with the aim of Isolation and characterization of Nitrogen Fixing Bacteria. The occurrence of Nitrogen Fixing Bacteria from root nodule of pea, white chickpea and red chickpea were investigated. Nitrogen fixing bacteria was isolated from root nodule of pea, white chickpea and red chickpea. The isolates were grown on yeast extract – mannitol agar (YEMA), and the morphologic characterization was done by Gram stain. A total of 21 isolates were isolated on Yeast Extract Mannitol (YEMA) agar medium. The isolates were circular, and irregular in form with smooth surface; entire, colony margins; with light pink coloured. The identification of isolated pure cultures through colony morphology analysis, cellular morphology and biochemical properties are including gram staining (negative), catalase test (negative), Methyl red test (negative), voges proskaeur test (positive), citrate utilization test (positive), starch hydrolysis test (positive) and mannitol salt agar (positive). Among the 21 bacterial isolates isolated, 18 were shown the characteristic of rhizobia. The effect of these 18 isolates those shows the characteristics of rhizobia were performed and all of them are significant, while compared with controls. These isolates will be useful to produce efficient bio fertilizers for Agriculture.

Microbiological and Physico-Chemical Characteristics of Black Tea Kombucha Fermented with a New Zealand Starter Culture.

Kombucha is a popular sparkling sugared tea, fermented by a symbiotic culture of acetic acid bacteria (AAB) and yeast. The demand for kombucha continues to increase worldwide, mainly due to its perceived health benefits and appealing sensory properties. This study isolated and characterised the dominant AAB and yeast from a starter culture and kombucha broth after 0, 1, 3, 5, 7, 9, 11, and 14 days of fermentation at ambient temperature (22 °C). Yeast and AAB were isolated from the Kombucha samples using glucose yeast extract mannitol ethanol acetic acid (GYMEA) and yeast extract glucose chloramphenicol (YGC) media, respectively. The phenotypic and taxonomic identification of AAB and yeast were determined by morphological and biochemical characterisation, followed by a sequence analysis of the ribosomal RNA gene (16S rRNA for AAB and ITS for yeast). The changes in the microbial composition were associated with variations in the physico-chemical characteristics of kombucha tea, such as pH, titratable acidity, and total soluble solids (TSS). During fermentation, the acidity increased and the TSS decreased. The yield, moisture content, and water activity of the cellulosic pellicles which had developed at the end of fermentation were attributed to the presence of AAB. The dominant AAB species in the cellulosic pellicles and kombucha broth were identified as Komagataeibacter rhaeticus. The yeast isolates belonged to Debaryomyces prosopidis and Zygosaccharomyces lentus.

Effect of Carrier Materials, Coinoculation and Sterilization on Survival of Plant Growth Promoting Microbes

The study was conducted to investigate diverse carrier materials out of agricultural and environmental waste, that plays a role in maintaining the shelf life of plant growth promoting microbes (PGPM) at room temperature for locally produced inoculants in Malawi. Five different formulations divided into sterilized and unsterilized were prepared, using different carrier materials namely; rice bran plus plant extract (RBP), biochar plus plant extract (BP), Filter mud plus plant extract (FMP), rice bran, biochar and plant extracts (RBCP), filter mud, biochar and plant extracts (FMBP). Carrier materials were packed in polyethylene pack (six per each treatment), thereafter each treatment was divided into sterilized and unsterilized. Each treatment was inoculated with either single or multiple inoculants. Survival of PGPM, was based on colony forming units (CFU) on specific selective media namely: modified yeast extract mannitol, pikovskaya’s, Alexandria and basal media for nitrogen fixing microbes, phosphate, potassium and zinc solubilising media respectively. Results revealed that encapsulated formulation of based combination formulation of RBCP in both single and multiple inoculants exerted high stable numbers of PGRM along the storage compared to other formulations. The results also show that unsterilized formulations exert high numbers compared to sterilized which is as a result of hydrogen peroxide accumulation during sterilization. The study reveals that filter mud based formulations currently used in both single and multiple inoculants is not favorable for local environments because microbial numbers decrease after 20 days at room temperature. This makes filter mud formulations usage not favorable for rural smallholder farmers with no refrigeration facilities.

Isolation of Peanut (&amp;lt;i&amp;gt;Arachis hypogaea&amp;lt;/i&amp;gt; L.) Nodulating Rhizobia and Assessment of Their Phosphate Solubilizing Activity

Phosphate-solubilizing bacteria can enhance the dissolution of insoluble phosphorus in the soil, promoting the availability of soluble phosphorus. Thus, their application can reduce the use of chemical fertilizers and ease sustainable agriculture. The study aimed at isolating and assessing the phosphate solubilizing activity of peanut rhizobia isolated from root nodules of peanut in three Cameroonian soils (Douala, Bafoussam and Ebolowa). Rhizobia were trapped by seeding peanut in plastic pots containing different soils. 45 days later, at the flowering time, root nodules were harvested. From these nodules, rhizobia were isolated, purified on Yeast Extract Mannitol Agar (YEMA) medium and authenticated by inoculating them on sterile sand containing peanut plants and watered with a nutrient solution without nitrogen. The phosphate solubilizing activity of the rhizobia isolates was then assessed in Modified Mineral Salt Medium (MMSM) containing bromocresol green and where the soluble phosphate was replaced by insoluble inorganic phosphates from Cameroon, Algeria, Senegal and tricalcium phosphate in both solid and broth media. The results were analysed statistically by one-way ANOVA using SPSS. A collection of twenty-five isolates was constituted among which 04 from Douala, 12 from Bafoussam and 09 from Ebolowa. All isolates were distinct morphologically. There was significant solubilization of inorganic phosphate in both solid and broth media (p<0.05). Isolated bacteria were characterized as being phosphate solubilizers with values ranging from 1.75 (AhBf1 on Algeria rock phosphate) to 18.9 mg/L (AhDa3 on Algeria rock phosphate). The Algeria rock phosphate was the most solubilized by peanut nodulating bacteria, followed by the tricalcium phosphate, the Senegal rock phosphate and the Cameroon rock phosphate. The solubilizing activity of inorganic phosphates in the broth medium was associated with a global decrease in the pH of the culture medium. The peanut nodulating rhizobia isolates that show the best solubilizing capacity could alleviate the problem of phosphorus availability in agricultural soils.

Exploring potential soybean bradyrhizobia from high trehalose-accumulating soybean genotypes for improved symbiotic effectiveness in soybean.

Drought is the most important factor limiting the activity of rhizobia during N-fixation and plant growth. In the present study, we isolated Bradyrhizobium spp. from root nodules of higher trehalose-accumulating soybean genotypes and examined for moisture stress tolerance on a gradient of polyethylene glycol (PEG 6000) amended in yeast extract mannitol (YEM) broth. In addition, the bradyrhizobial strains were also evaluated for symbiotic effectiveness on soybean. Based on 16S rDNA gene sequences, four bradyrhizobial species were recovered from high trehalose-accumulating genotypes, i.e., two Bradyrhizobium liaoningense strains (accession number KX230053, KX230054) from EC 538828 and PK-472, respectively, one Bradyrhizobium daqingense (accession number KX230052) from PK-472, and one Bradyrhizobium kavangense (accession number MN197775) from Valder genotype having low trehalose. These strains, along with two native strains, viz., Bradyrhizobium japonicum (JF792425), Bradyrhizobium liaoningense (JF792426), and one commercial rhizobium, were studied for nodulation, leghaemoglobin, and N-fixation abilities on soybean under sterilized sand microcosm conditions in a completely randomized design. Among all the strains, D-4A (B. daqingense) followed by D-4B (B. liaoningense) was found to have significantly higher nodulation traits and acetylene reduction assay (ARA) activity when compared to other strains and commercial rhizobia. The bradyrhizobia isolates showed plant growth promotion traits such as indole acetic acid (IAA), exopolysaccharide (EPS), and siderophore production, phosphate-solubilizing potential, and proline accumulation. The novel species B. daqingense was reported for the first time from Indian soil and observed to be a potential candidate strain and should be evaluated for conferring drought tolerance in soybean under simulated stress conditions.

Endophytic phosphate solubilization and potential nitrogen-fixing bacteria in the leaf and root of rice planted on the conventional wetland

Endophytic bacteria inhabit internal plant tissue and generally promote plant growth, showing no external sign of infection or negative effect on their host plant. Endophytes play diverse roles including nutrient acquisition, production of phytohormones and siderophores, protection against abiotic stresses. The purpose of this study was to isolate and characterize endophytic bacteria which have the specific capability of the acquisition of nutrients especially Phosphate Solubilizing Bacteria (PSB) and potentially Nitrogen Fixing Bacteria (NFB) from the leaf and root of rice planted on the conventional wetland of Inceptisol. Isolation of endophytic bacteria was conducted by sterilizing the surface of plant samples and then inoculating using the spread plate method on pikovskaya and yeast extract mannitol agar media. The growing bacterial colonies on the media showed that the diversity and population density of endophytic PSB in the root was higher than in the leaf tissue, namely 4 types of isolates with 1,526x105 CFU/g in the root and 2 types of isolates with 0.0395x105 CFU/g in the leaf. On the other hand, the diversity of endophytic potentially NFB in the leaf was higher than in the root tissue namely 5 and 3 types of isolates, but the population density was higher in the root at the level 11,55x105 CFU/g than in the leaf at 5,976x105 CFU/g. The next research is necessary to compare endophytic bacteria from rice planted in inorganic and organic cultivation systems, and continued with the examination of the effect of inoculation of those endophytic bacteria to the targeted crops.

Effects of Indigenous and Commercial Rhizobia on Growth and Nodulation of Soybean (Glycine max L) under Greenhouse Condition

Background: Soybean (Glycine max L.) is the most vital grain legume crop rich in protein and oil. The inoculation of rhizobia with soybean plays a very important role in increasing soil fertility via its contribution to biological nitrogen fixation. Objective: This study focuses on the evaluation of indigenous and commercial rhizobia on soybean nodulation and growth parameters. Methodology: Soil samples were collected from five districts for nodule trapping. The rhizobia were isolated using ‘plant induction following the standard procedures. The greenhouse experiments were arranged in a completed randomized design with three replications and two control units. The data were collected for plant height, nodule number, nodule dry weight, shoot dry weight, root length; root dry weight, total nitrogen and nitrogen-content. Results: The entire isolates were found gram-negative, without absorbing congo-red and did not grow on peptone glucose agar media. Slow grower isolates turned bromothymol blue with yeast extract mannitol agar medium into a moderately deep blue color but fast grower changed to yellow color. All isolates were tested on the sand induced nodule and were significantly superior to the negative control in terms of plant height, shoot dry weight, and nodule dry weight. The shoot dry weight of soybean rhizobial isolates on the sterilized sand experiment was ranging from 1.6 to 2.2g per plant and it was a highly significant correlation to the nodule number, nodule dry weight and root dry weight. Conclusion: The indigenous isolates were highly competent to all commercial rhizobia. This study encourages further evaluation of the field and molecular characteristics.

OPTIMISATION OF MEDIA FOR PRODUCTION OF COST- EFFECTIVE RHIZOBIUM [BIOFERTILIZER

Rhizobium is a soil habitat, gram negative bacterium associated symbiotically with the roots of leguminous plants. Rhizobium helps in the process of nitrogen fixation. Screening and selecting the most effective strain play a key role in the process of biological nitrogen fixation. The present work was undertaken to bring into light different characteristics, growth, isolation, and secretion ofrhizobial strains (bradyrhizobium). These are found in the root region of the leguminous plants where it forms nodules and fix nitrogen. The study revealed that the species used was non-spore forming, rod-shaped, motile, aerobic, gram- negative soil bacterium. These rod-shaped bacteria are 0.8um in diameter and 2um in length, and often have flagellae. These species are non-pathogenic to humans. The rhizobium bacteria were grown on three different types of medias namely – nutrient broth, CRYEMA( Congo Red Yeast Extract Mannitol Agar), and modified media containing jaggery. The common ingredients of the culture media includedPeptone, Meat Extract, Mineral Salts, Carbohydrates and Water. Growth analysis, substrate estimation and biomass estimation was done and yield coefficient was calculated. Rhizobium was then applied as a biofertilizer for good improvement in plant growth and yield. Key Words: Biofertilizers, Biological Nitrogen Fixation, Bradyrhizobium, Inoculants, Leguminous plants, Optimized Media.

Detection of Family Specialty for Microbacterium sp. AJ-Z Isolated from Fenugreek (Trigonella foenum-graecum) Root Nodules

Microbacterium sp. AJ-Z was isolated from fenugreek (Trigonella foenum-graecum) root nodules on Yeast Extract Mannitol (YEM) medium. Colonies of the bacteria isolates grown were rod shape, whitish, translucent, sticky nature. The results showed responded of the fenugreek seedlings grown on Nitrogen free medium (NF) to inoculated with Microbacterium sp. AJ-Z isolate at 30 min. and successful to form nodules its roots in the rate of 70% after 7 days with rate number of nodes/seedling was 2.9 superiority on the other which grown on Murashige and Skoog (MS) medium and 0.7% agar. Nodules produced have a spherical shape, pinkish and indeterminate in growth and after a few days, its shape becomes elongated.

Characterization of Plant Growth Promoting Rhizobacteria From Seasonal Flower Beds

The present investigations were carried out to screen the PGPR isolates from five separate seasonal flower beds (Catharanthus roseus, Portulaca grandiflora, Celosia argentea, Gomphrena globosa and Impatiens balsamina) of Curzon Hall, University of Dhaka. The bacterial load of the collected soil samples ranged in between 7.60 ± 6.01 × 106 and 9.49 ± 5.44× 108 cfu/g, 5.34 ± 4.06×106 and 13.4 ± 4.8×106 cfu/g and 1.01 ± 0.59×106 and 1.19 ± 0.95×108 cfu/g on Nutrient Agar (NA), Luria-Bertani (LB) and Yeast Extract Mannitol Agar (YEMA), respectively. All the selected eight isolates were Gram positive and rod shaped. All isolates were found to be IAA producer and 7 showed varying levels of phosphate solubilizing activity. IAA production and phosphate (P) solubilization of the selected isolates ranged in between 9.76 ± 5.98 to 17.99 ± 1.865 U/ml, and 1.17 ± 0.59 to 1.84 ± 0.499 mg/l. Maximum production of both IAA and phosphate solubilization was achieved in 24h of incubation period at 37°C and pH 7.0. Germination test against Mung Bean (Vigna radiata) revealed positive plant growth promoting activities and could be used as PGPR inoculant. Dhaka Univ. J. Biol. Sci. 31(2): 321-328, 2022 (July)

Diazotrophic Bacterial Response to Herbicide Toxicity: In vitro Analysis

Diazotrophic bacteria play critical role in biological nitrogen fixation (BNF), and the application of herbiced significantly affect growth and activities of these bacteria. To investigate this, 1.0 ml of broth stock culture containing 2.9 x 105 cfu/ml and 2.6 x 106 cfu/ml of Azotobacter and Bradyrhizobium, respectively were inoculated into 10.0 ml of their respective growth medium [ TDC broth, and Yeast extract mannitol broth (YEMB)] containing 0, 0.5, 1.0, 1.5 and 2.0 % v/v of the respective herbicides, atrazine, glyphosate, paraquat and 2,4-D. Thereafter, plate counts of the diazotrophs for each concentration was made at 24, 48, 72 and 120 h intervals using spread plate method on TDC agar and YEMA after incubation at room temperature (30 ± 2 ℃) for 72 h. The LC50 of the respective herbicides for Azotobacter and Bradyrhizobium was determined at 120 h using Probit analysis. Results showed that all tested concentrations except control, retarded diazotrophic bacterial population growth. Growth reduction increased progressively with increased concentrations of herbicides (P &lt; 0.05). In general, herbicides were found to suppress the growth of diazotrophs by 29.7 – 100 %. The LC50 indicated symbiotic Bradyrhizobium displayed greater sensitivity to tested herbicides than free-living Azotobacter (P &lt; 0.05). Conclusively, herbicides suppressed diazotrophic bacterial growth.