Soil Bacterial Populations Research Articles

Comparative Study of Pesticide Resistant Soil Microbes from Mango Farms of Pallam and Nenmeni Panchayath in Muthalamada, Palakkad

Abstract: In the current study a comparison between the soil bacterial population of Mango farm polluted and non-polluted with pesticide were carried out. The study showed that different insecticides were used in each growing season and that farmers apply a lot of pesticides to control pests of mango. Pesticides are applied once every three or four days. The mixtures for insecticides and fungicides used and at least three types of variations with doses of 30–40 ml for each type. Excessive use of pesticides has been known to be hazardous to the environment, affect soil fertility as well may impart toxicity in living beings including beneficial bacteria. Major bacterial genera found in the soil includes; Bacillus, Pseudomonas, Micrococcus, Serratia Proteus, Enterobacter. Bacterial resistance towards the pesticides used in the mango farms were studied using pesticides Hamla, Larincare and Zipvin in various concentrations like (2 μl/ml) (4 μl/ml) (6 μl/ml).It has been found that all the four bacteria can grow in the presence of pesticides indicating all the four bacteria is resistant to all the tested pesticides.

Decay of Root Debris after Harvesting American Ginseng (Panax quinquefolius) and Changes in Soil Chemistry and Microbiology

Commercial harvesting of American ginseng (Panax quinquefolius) results in root debris in the soil, but the rate of decay is unknown. In this study, post-harvest root debris decayed mostly over the fall and winter, with almost no ginseng debris remaining in the soil by late spring of the following year. However, a small number of intact pencil-shaped roots were able to survive after harvest and sprout the following spring without any evidence of root decay. Root rot lesions were observed, which included many associated with the root rot pathogen Ilyonectria mors-panacis, with disappearing root rot symptoms observed in the following spring. Ginsenosides in soil were highest just prior to harvest, declining until an increase the following spring. Soil bacterial and fungal populations changed over time after harvest with several peaks in bacterial populations mostly in the fall, but this was less clear for fungal populations, which were dominated by only a few taxa. Harvesting ginseng can leave considerable debris in the soil, impacting its chemistry and microbiota. Ginseng replant disease, where the second crop shows high levels of root rot due to I. mors-panacis infection compared to low levels in the first crop, could be related to the decay of post-harvest crop debris, but additional research is needed to demonstrate this.

Soil Bacteriome Resilience and Reduced Nitrogen Toxicity in Tomato by Controlled Release Nitrogen Fertilizer Compared to Urea

Controlled release fertilizers (CRFs) mitigate negative effects of high nitrogen (N) fertilization rates, such as N toxicity and soil N loss. However, it is unknown if potentially toxic rates of CRF and quick release fertilizer differentially affect soil bacterial communities. To examine potential N toxicity effects on soil microbial communities, we grew tomato (Solanum lycopersicum “Rutgers”) for eight weeks in soils that were fertilized with high levels of quick release or controlled release urea and in soils with either low or high initial microbial N competitor populations. In both soils, we observed N toxicity in urea-fertilized tomatoes, but toxicity was ameliorated with CRF application. Controlled release fertilization increased soil N retention, thereby reducing soil N loss. While N toxicity symptoms manifested in the plant, the soil microbiome was only minorly affected. There were subtle differences in soil bacterial populations, in which nitrifying bacteria accumulated in soils fertilized at high N rates, regardless of the type of N fertilizer used. Ultimately, CRF reduced plant N toxicity symptoms but did not change the soil microbiome compared to quick release urea. These results show that while there are clear benefits of CRF regarding N toxicity tolerance on crops, the soil microbiome is resilient to this abiotic stressor.

Effects of Vegetation Types and Seasonal Dynamics on the Diversity and Function of Soil Bacterial Communities in the Upper Reaches of the Heihe River

The process of interaction between the plant and soil microbial communities holds the key to understanding the biogeochemical cycle and preserving the stability of vegetation ecosystems. Owing to this significance, the primary goal of this research was to give a starting point and reference methods to restore local vegetation. The vegetation distribution in the mountainous area of the upper reaches of the Heihe River Basin had notable vertical zonality, which was characterized by five typical vegetation types, including cushion vegetation(CV), herbage meadow(HM), forest steppe(FS), mountainous steppe(MS), and desert grassland(DG). The organization and diversity of soil bacterial communities in various vegetation types were examined using high-throughput sequencing techniques in both the winter and summer seasons. Sampling sites were chosen in each of the five common vegetation types in turn. Additionally, based on the FAPROTAX database, the predicted functions of microbial communities were evaluated for different vegetation types and seasons. The redundancy analysis and structural equation model were also used to investigate the primary environmental elements and uncover the mechanisms affecting the soil bacterial populations. The findings revealed that:① the physical and chemical properties of soil differed significantly among vegetation types and seasons, and the property indices varied dissimilarly with depth. In particular, the soil water content(SWC) and nutrient content of total organic carbon(TOC) and total nitrogen(TN) were significantly higher in forest grassland(FS). ② The divergences of α-diversity indices among seasons(P<0.05) were greater than that of vegetation types(P>0.05). The Chao1 index measuring the abundance of the bacterial community was higher in winter. According to the Shannon index, the species of the bacterial community were dispersed in a "W" shape in the summer and a "hump" form in the winter with altitude. ③ The predominant phyla of the bacterial community, composed of Acidobacteria, Proteobacteria, and Actinobacteria, did not significantly differ from one another. However, the organization of the bacterial community presented a significant variation seasonally at the genus level. ④ The primary functions of the soil bacterial population, which largely consisted of chemoheterotrophy, nitrification, and aerobic ammonia oxidation, were not significantly different among vegetation types and seasons. ⑤ The key factors affecting soil bacterial communities at the genus level varied significantly among seasons, with soil temperature(ST), total organic carbon(TOC), and pH in winter and soil water content(SWC), carbon-nitrogen ratio(C/N), and pH in summer. ⑥ Synergized by interrelated environmental factors, soil physical and chemical features exerted a more direct impact on the diversity and functionality of bacterial communities compared with vegetation types, including significantly changing the abundance of Acidobacteria and Bacteroidetes, as well as the role of nitrification and ammonia oxidation. Hence, improving the carbon and nitrogen contents in soil nutrients would help to enhance the diversity and function of bacterial communities. The findings of this study provided a model for determining the mechanism of regional vegetation degradation and preserving the stability of alpine ecosystems in this area by revealing the seasonal distribution pattern of bacterial communities and the key biological processes beneath the typical vertical vegetation band in the upper reaches of the Heihe River.

The Shallot Growth and Yield from True Shallot Seed using Biochar, Compost, and Organic Pesticide in Wanasari, Brebes Regency

The practice of environmentally friendly shallot cultivation is nowadays widely applied by farmers, beside reducing environmental contamination and producing agricultural products that are safe for consumption, it can also increase shallot production. This study aimed to determine the effect of biochar, compost, and organic pesticides on the growth and yield of shallot, and the activity of microorganisms in the soil. The study was conducted in Klampok Village, Wanasari, Brebes Regency from January to July 2020 using a complete randomized block design with nine treatments which were a combination of biochar, compost, organic pesticides, recommended dose of pesticides, and farmers’ dose of pesticides. The shallot seed used was the Bima Brebes variety. Soil characteristics, compost nutrient contents, plant growth, shallot yield, and total soil bacteria population were measured. The study showed that the yield of shallot was 16.7 tons/ha obtained from adding compost and recommended doses of pesticides. The treatment of biochar, compost, and organic pesticides, although it has not been able to increase the growth and yield of shallot, it can be applied for shallot cultivation as it can increase the total bacterial population of soil, reduce the use of chemical pesticides, reduce production input costs, and environmentally friendly.

Nitrogen, Rhizobium and molybdenum for higher soil bacterial population, N uptake and productivity of lentil (Lens culinaris) grown under rice (Oryza sativa)-fallow conditions

A field experiment was conducted during the winter (rabi) seasons of 2014–15, 2015–16 and 2016–17 in loamy soils of the Regional Agricultural Research Station, Assam Agricultural University, Shillongani, Assam, to study the effect of varying doses of nitrogen, Rhizobium and molybdenum on bacterial population in soil, N uptake, yield attributes, grain yield and economics of lentil (Lens culinaris Medikus spp. culinaris) grown after the harvesting of winter rice (Oryza sativa L.) variety ‘Gitesh’. Soil bacterial population increased with the increase in nitrogen doses. The crop grown using seeds inoculated with Rhizobium @ 50 g/kg seed and sodium molybdate @ 1 g/kg seed along with 100% of recommended dose (RD) of N (15 kg/ha) accrued in the highest bacterial population in the soil at harvesting. Seed inoculation with Rhizobium and sodium molybdate led to considerably higher bacterial population build up in soil than seed inoculation with Rhizobium and sodium molybdate separately. Nitrogen uptake by lentil got reduced with decreasing N doses, being 28.54 kg/ha under RD of N and 28.03 kg/ha under 75% of recommended N. The treatment combinations involving RD and 75% of RD of N (11.25 kg/ha) and seed inoculation with Rhizobium and sodium molybdate recorded 35.16 kg/ha and 34.97 kg/ha N uptake respectively. These 2 treatment combinations ultimately accrued in higher values for plant height, pods/plant, seeds/pod and 100-seed weight and significantly higher grain yield (928.90 and 868.89 kg/ha respectively) as compared to all other treatment combinations. Benefit: cost ratios under these 2 treatment combinations were 2.18 and 2.09 respectively. The treatment combinations were tested for maximizing lentil production utilizing rice-fallows and farmers’ acceptability in farmers’ fields during rabi 2017–18 through 3 Krishi Vigyan Kendras (KVK) in Upper Brahmaputra Valley (UBV) in Jorhat district, Central Brahmaputra Valley (CBV) in Nagaon district and Lower Brahmaputra Valley (LBV) in Nalbari district of the state. The RD of N + seed inoculation with Rhizobium and sodium molybdate yielded the highest (5.8–8.2 q/ha) at all the locations closely followed by 75% RD of N + Rhizobium + sodium molybdate (5.93–7.25 q/ha).

Effect of Liquid Biofertilizers on Productivity, Quality and Soil Biota of Fodder Sorghum

The field experiment was conducted during Rabi season of 2022 on sandy clay loam soils at wetland farm of the S.V. Agricultural College, Tirupati, Andhra Pradesh, India, to study the effect of liquid biofertilizers on productivity, quality, and soil biota of fodder sorghum. The treatments were allocated in randomized block design and replicated thrice. The soil was neutral in reaction (6.9 pH), low in available nitrogen (115 kg ha-1), medium in available phosphorus (29 kg ha-1) and low in available potassium (156 kg ha-1) status. The initial soil contains bacteria (13.08 X 107 CFU g-1 soil), fungi (4.04 X 104 CFU g-1 soil) and actinomycetes (1.54 X 103 CFU g-1 soil). The results revealed that the maximum green (32.1 t ha-1) and dry (13.0 t ha-1) fodder yield as well as crude protein (7.3%) were obtained with the application of 75% RDF + Azospirillum + PSB + KSB (Both seed &amp; soil application). Furthermore, this treatment produced a significantly higher soil bacterial (23.2 X 107 CFU g-1 soil), fungal (13.7 X 104 CFU g-1 soil) and actinomycetes (10.3 X 103 CFU g-1 soil) population at harvest.

Selüloz ve PLA Biyopolimer Nonwoven Malçların Toprak Sağlığına Etkisi

The nonwoven mulches produced from regenerated viscose and PLA fibres as well as conventional agro foil were placed on the soil by randomly arranged blocks of four replication plots. After 50 days, the soil samples beneath each mulch and on the control field were collected, where the bacteria and fungi population as well as the physio-chemical properties of the soil were measured. The severe reduction in bacterial population in soil under the agro foil and mulches made of PLA fibres occurs due to the prevalence of high soil temperature. The bacterial population of soil beneath the mulches made of viscose fibre significantly increased due to favourable anaerobic conditions, respectively soil temperature and moisture. Under all mulches, compared to the control field, a higher fungal population was observed. The fungal population under the nonwoven mulch produced by viscose fibres was 161% higher in comparison to the control field. The available nutrient contents of soils under the nonwoven mulches were higher compared to the control field. The control field showed higher available nutrient contents of soil than the field covered by conventional agro foil.&#x0D; The results of the study reveal that usage of nonwoven mulches made of viscose fibres is most appropriate for short-term mulching application since successfully increases microbial population and improves the physio-chemical properties of soil.

Long-Term Fertilizer Optimization with Slow-Release and Organic Fertilizers Improves N Use Efficiency and Soil Bacterial Populations in Paddies

Long-Term Fertilizer Optimization with Slow-Release and Organic Fertilizers Improves N Use Efficiency and Soil Bacterial Populations in Paddies

Combined benefits of fermented washed rice water and NPK mineral fertilizer on plant growth and soil fertility over three field planting cycles

Washed rice water (WRW) is the leftover water after washing rice grains and is usually discarded. However, WRW contains nutrients leached from rice, making it a potential plant fertilizer. Reusing WRW promotes better water governance, particularly in the face of increased freshwater needs due to population expansion and climate change. Recent experiments in rain shelters have demonstrated the advantages of using WRW as fertilizer. Building on this, our study assessed WRW's efficacy in an open field against NPK fertilizer, both individually and in combination. The treatments were: R3 (3-day fermented WRW), N1 (full recommended NPK rate), N0.5R3 (half NPK rate and R3), and CON (tap water only). These treatments were tested over three consecutive planting cycles of choy sum (Brassica chinensis var. parachinensis) vegetable. At the end of each planting cycle, measurements were taken for the plant's growth, nutrient content and uptake, as well as various soil chemical properties and bacterial population. Plants were watered daily with 5 mm WRW (R3 and N0.5R3) or tap water (N1 and CON). N0.5R3 showed the best results in terms of plant growth, nutrient content, uptake, and soil nutrient levels. N0.5R3 supplied the most nutrients, especially N, P, and K. Increased plant growth also led to increased plant uptake of nutrients, including micronutrients. Macronutrients had a greater impact on plant biomass than micronutrients, as R3 and N1 had similar results. R3 soils had higher bacterial populations but were more acidic than N1 soils. The negative effect of NPK on bacteria was partially offset by combining NPK with WRW as N0.5R3. No carryover effects were observed, likely because of the high nutrient leaching from heavy rains. These findings confirm WRW's is an effective fertilizer in open fields, but measures like surface mulching are crucial to minimize nutrient leaching prior to its use.

Physicochemical and microbial alterations in crude oil-contaminated soil samples

Environmental pollution is becoming an issue of concern due to its negative impact on the living and non-living components of the environment. Crude oil and its products are the major sources of environmental pollution that renders negative impact on the soil mineral components and microorganism. This study was thus carried out to determine the effect of crude oil on soil physicochemical properties, bacterial and fungal population. The experiment lasted for 42 days and the analysis were carried out at days 0, 14, 28 and 42 using standard protocols. Results obtained show significant changes (P ≤ 0.05) in hydrocarbons and other physicochemical parameters such as pH, nitrate, electrical conductivity, sodium ion, calcium ion, phosphate and magnesium ion, when the control was compared with crude oil contaminated soil. Also, soil bacterial and fungal count decreased significantly (P ≤ 0.05) with increasing concentrations of crude oil indicating its toxicity to soil microbial consortium. However, results also showed that hydrocarbon-degrading microorganisms strived at higher concentrations but insignificantly (P ≤ 0.05) in comparison with the control. Owing to the result obtained in this study, crude oil exploration should be properly managed to prevent spillages that negatively impact on the environment.

Carbendazim Modulates the Metabolically Active Bacterial Populations in Soil and Rhizosphere

Carbendazim Modulates the Metabolically Active Bacterial Populations in Soil and Rhizosphere

Isolation and Molecular Identification of Cellulase producing bacteria from soil and litter in Veerakkal forest area, The Western Ghats, India

The cellulolytic bacterial strains were screened from both soil and litter samples in different study sites of Veerakkal forest, Manar beat, The Western Ghats, India. In the current investigation, out of 64 and 48 differentiated total purified isolates, 53 soil isolates and 34 litter isolates were screened based on the CMC method. The percent wise calculation indicated that 82 % were cellulase positive while 18 % were negative in soil isolates. Likewise, 70 % of them were positive while 30 % were negative cellulase strains in litter isolates. The average hydrolysis capacity (HC) values ranged between 1.67 to 3.25 cm. The highly potential cellulolytic bacterial isolates viz. Bacillus thuringiensis, Bacillus licheniformis, Bacillus cereus, Bacillus sporothermodurans, Bacillus circulans, Bacillus albus, Bacillus amyloliquefaciens, Lysinibacillus sphaericus and Bacillus mobilis were identified from soil. Likewise, the litter cellulolytic bacterial species such as Bacillus sp., Lysinibacillus macroides, Bacillus paramycoides, Solibacillus silvestris, Pseudomonas stutzeri, Bacillus toyonensis, Bacillus subtilis, Bacillus pacificus, Bacillus flexus, Bacillus paranthracis and Pseudomonas putida were identified. The cellulolytic bacterial population was higher during the monsoon because of the presence of higher moisture content in leaf litter. However, the cellulolytic bacterial population of soil was higher during the pre-monsoon season because of the continuous breakdown of litter which inhaled more cellulolytic strains in the soil. Finally, it was concluded that corresponding with seasonal changes, the cellulolytic bacterial community also changed and it plays a significant role in the mineralization process.

Response of soil bacterial populations to application of biosolids under short-term flooding

Biosolids are applied to agricultural land as a soil conditioner and source of crop nutrients. However, there is concern that bacteria from biosolids may become established in soils, particularly if that soil becomes water-logged. This study examined the microbial community of arable soils cultivated with barley under different applications of biosolids (0, 24t/ha, 48t/ha) in laboratory mesocosms which simulated a 10-day flood. Nutrients (P and N) and organic matter in the soil increased with application rate, but plant growth was not affected by biosolid application. The biosolids contained 10× more genetic material than the soil, with much lower bacterial diversity, yet application did not significantly change the taxonomy of the soil microbiome, with minor changes related to increased nutrients and SOM. Anaerobic conditions developed rapidly during flooding, causing shifts in the native soil microbiome. Some bacterial taxa that were highly abundant in biosolids had slightly increased relative abundance in amended soils during the flood. After flooding, soil bacterial populations returned to their pre-flood profiles, implying that the native microbial community is resilient to transient changes. The short-term changes in the microbiome of biosolid-amended soils during flooding do not appear to increase the environmental risk posed by biosolid application.

Influence of Beneficial Bacterial Inoculation on Nitrogen Concentration and Tomato Seedling Growth Under Glasshouse Conditions

Many types of soil bacteria through antagonistic activity, thrive in the rhizosphere of plants or surround the tissues of plants and encourage plant development and reduce the nematode population. Bacteria as such are commonly known as Plant Growth-Promoting Rhizobacteria (PGPR). The purpose of this research was to determine Bacillus spp. inoculations impact on tomato seedling development with varying rates of chemical nitrogen-fertilizer. To minimize the recommended quantity of N fertilizer for tomato seedling development, a small pot experiment with selected PGPB was undertaken with varying amount of N fertilizer. Plant growth-promoting bacteria (PGPB) labeled as UPMB10 and UPMRB9 (identified as Bacillus subtilis and Bacillus tequilensis, respectively) were utilized as microbial inoculants because they showed a significant improvement in seedling growth and N concentration in tomato plant tissues in a pot culture investigation. These microbial inoculants significantly improved the development of the plants, stem length, root length, leaves number, dry weight of shoots (stem, leaves), dry weight of roots, SPAD value, N concentration in tissues, and soil bacterial population. Bacteria-treated seedlings with 50% N fertilizer significantly increased stem length (69.07%), root length (78.51%), leaves number (68.58%), shoots (92.45%, 90.39%, stem and leaves, respectively), roots (73.33%), SPAD value (50.31%), and N concentration in plant tissues (63.79%) as compared to the uninoculated control. The findings also showed that inoculation of the Bacillus spp. tomato seedlings could save up to 50 percent of the recommended rate of chemical N fertilizer without affecting tomato seedling growth. The findings of this study suggest that the amount of nitrogen fertilizer given during tomato seedling development can be reduced by half, resulting in increased soil health and reduced environmental pollution.

The effect of land management and organic matter inputs on bacterial population and soil nutrients across different types of agroforestry system

Abstract. Rinady MVP, Nuraini Y, Prayogo C, Arfarita N. 2023. The effect of land management and organic matter inputs on bacterial population and soil nutrients across different types of agroforestry system. Biodiversitas 24: 1333-1345. Different management of agroforestry systems changes crop composition and growth. This will affect organic matter inputs that become the source of food and energy for soil microorganisms. The soil organisms themself play an important role in amplifying soil biogeochemical processes and regulating soil reactions. This process allows the nutrients to be released into the soil and absorbed by the crop. This study aimed to examine the abundance of soil bacterial population and the changes in soil chemical properties (soil pH, total soil organic carbon (C), and total soil N (Nitrogen) under different land management and organic matter inputs. The determination of total organic C and total soil N was used by Walkey and Black and Kjedahl methods. Total Plate Count (TPC) techniques were employed to measure Total Bacteria Population (TBP) and Total Cellulolytic Bacteria (TCB). The Randomized Complete Block Design was used along with the 5% Tukey's test to examine the significant effect of the treatments. These treatments consisted of various agroforestry system as follow: (i) pine-coffee agroforestry system (PK), (ii) pine-banana agroforestry system (PPs), (iii) pine-cardamom agroforestry system (PR), (iv) pine-vegetable agroforestry system (PS), (v) mixed garden (KC), and (vi) citrus (LJ). Each treatment was repeated four times to obtain 24 experimental plots using a size of 20 m x 20 m. The results showed that the highest organic C and N content was obtained at the PK (agroforestry of pine at 41 years and coffee at 11 years old) plot, which was about 6.64% and 0.56%. Those parameters strongly correspond to the greatest soil bacteria population and soil cellulolytic bacteria population at the value of 1,71 x 105 CFU/g and 4,24 x 104 CFU/g, resulting from the greatest quantity of in-situ litter accumulation at PK plot to reach about 201.35 g. The dry weight value of litter in situ at the PK plot is greater than that of the PS and LJ plots by 81% and 87%. A power equation followed the relationship between soil organic C and the total bacteria population. A similar trend has been observed between total soil Nitrogen and total bacteria population. We concluded that changes in different management could affect soil chemical conditions and the changes in the total population of soil bacteria and cellulolytic soil bacteria.

Effects of Carbon-Based Fertilizer on Soil Physical and Chemical Properties, Soil Enzyme Activity and Soil Microorganism of Maize in Northeast China

The soil environment is an important factor that affects the growth of maize. Our study discusses the effect of carbon-based fertilizer on the rhizosphere soil microenvironment. Xianyu 335 and Jingke 968 maize varieties were selected, and six treatments were set up as follows: no fertilizer, chemical fertilizer, or carbon-based fertilizer (3 t/hm2, 3.75 t/hm2, 4.5 t/hm2, and 5.25 t/hm2). The results showed that the carbon-based fertilizer significantly reduced the soil pH value in the late growth stage. Carbon-based fertilizer can significantly improve the conductivity of soil solution. On 8 July (jointing stage), the conductivity of the two varieties of soil was the highest at 3.75 t treatment, 259.38% and 169.26% higher than that of chemical fertilizer, respectively. Carbon-based fertilizer significantly increased the soil carbon flux. The soil carbon flux of Jingke 968 showed a trend of first rising and then falling with the increase in the application amount of carbon-based fertilizer. On 8 July (jointing stage) and 28 July (tasseling stage), the 4.5 t treatment reached the maximum value, and on 16 August (early filling stage) and 4 September (waxy stage), the 3.75 t treatment reached the maximum value. Carbon-based fertilizer significantly increased the content of nitrate nitrogen, ammonium nitrogen, available phosphorus, and available potassium in the topsoil. Carbon-based fertilizer had a significant effect on soil enzyme activity and significantly increased soil neutral phosphatase activity in the late growth stage. On 16 August (early stage of grouting), β-Glucosidase activity was significantly higher in 3 t and 3.75 t treatments than other treatments in Xianyu 335 and Jingke 968. The activity of α-Xylosidase reached the highest at 3.75 t. The activities of polyphenol oxidase and catalase reached their maximum at 5.25 t treatment on 4 September (waxy ripening) and 26 September (full ripening). Carbon-based fertilizer significantly increased the soil bacterial diversity index (Shannon index, ACE index and Chao1 index), but had no significant impact on the fungal diversity index, and significantly increased the abundance of soil bacterial and fungal populations.

Nutrients strengthen density dependence of per-capita growth and mortality rates in the soil bacterial community.

Density dependence in an ecological community has been observed in many macro-organismal ecosystems and is hypothesized to maintain biodiversity but is poorly understood in microbial ecosystems. Here, we analyze data from an experiment using quantitative stable isotope probing (qSIP) to estimate per-capita growth and mortality rates of bacterial populations in soils from several ecosystems along an elevation gradient which were subject to nutrient addition of either carbon alone (glucose; C) or carbon with nitrogen (glucose + ammonium-sulfate; C + N). Across all ecosystems, we found that higher population densities, quantified by the abundance of genomes per gram of soil, had lower per-capita growth rates in C + N-amended soils. Similarly, bacterial mortality rates in C + N-amended soils increased at a significantly higher rate with increasing population size than mortality rates in control and C-amended soils. In contrast to the hypothesis that density dependence would promote or maintain diversity, we observed significantly lower bacterial diversity in soils with stronger negative density-dependent growth. Here, density dependence was significantly but weakly responsive to nutrients and was not associated with higher bacterial diversity.

The bacterial population inhabiting a top-ranking High Background Radiation Area: A first-time report

Aim: To study the soil bacterial population inhabiting the High Background Radiation Area (HBRA) of Chavara-Neendakara placer deposits, Kerala, India. Methodology: The study was performed by culture-dependant methods involving isolation and characterization of microbes through plate culturing and sequencing the 16S rDNA primed PCR amplicons. Results: Histochemical observations and molecular taxonomic studies through BLAST search, multiple sequence alignment of the sequences and SeaView phylogenetic analyses, resulted in identification of 35 bacterial species belonging to 22 genera. Shannon-Simpson diversity-predominance indices, revealed an over-riding presence of Firmicutes (~60%) in the HBRA soil. Interpretation: The results reveal for the first time, the composition, structure and dynamics of the bacterial population inhabiting an HBRA. Key words: Chavara-Neendakara placer deposit, Firmicutes, Gini-Simpson Index, High background radiation area, Shannon index

Distribution and correlation of Soil bacterial population and chemical properties in salt affected landuses of Kaithal and Fatehabad district of Haryana

This study attempts to examine the relationship between soil bacterial population and physico-chemical properties of soil in Kaithal and Fatehabad district of Haryana. Soil pH in the study ranged from 7.7 to 10.32 in the selected sites. EC in the study ranged from 200 to 1780 μS/m at 25 °C. Organic carbon ranged from 0.10 to 1.32% in the present study. Majority of soil samples showed medium status of available nitrogen which ranged from 0.0005 to 0.02%. Soil phosphorus is most available for plant use at pH values of 6 to 7. Potassium content ranged from 0.001 to 0.05%. The present study revealed that bacteria isolated from bottom segment showed higher growth rate in anaerobic condition. A decreasing trend of total microbial population and organic carbon content of soil were found with increase in depth. The maximum number of bacterial colonies was observed at the depth of 0-30 cm. Gram’s staining Revealed that 0-30 cm depth was occupied by majority of Gram negative bacteria in Haryana. 30-60 cm depth was analyzed, there was a slight but significant difference in the bacterial population and majority were Gram positive. Simultaneously there was less variation with respect to colony morphology and pigment production as compared to the depth of 0-30 cm.