Inoculants of plant growth-promoting bacteria for use in agriculture

Introduced microorganisms are potentially powerful agents for manipulation of processes and/or components in soil. Fields of application include enhancement of crop growth, protection of crops against plant-pathogenic organisms, stimulation of biodegradation of xenobiotic compounds (bioaugmentation), and improvement of soil structure. Inoculation of soils has already been applied for decades, but it has often yielded inconsistent or disappointing results. This is caused mainly by a commonly observed rapid decline in inoculant population activity following introduction into soil, i.e., a decline of the numbers of inoculant cells and/or a decline of the (average) activity per cell. In this review, we discuss the available information on the effects of key factors that determine the fate and activity of microorganisms introduced into soil, with emphasis on bacteria. The factors addressed include the physiological status of the inoculant cells, the biotic and abiotic interactions in soil, soil properties, and substrate availability. Finally, we address the possibilities available to effectively manipulate the fate and activity of introduced microorganisms in relation to the main areas of their application.

Fate and activity of microorganisms introduced into soil.

Immobilized microbial cells have been used extensively in various industrial and scientific endeavours. However, immobilized cells have not been used widely for environmental applications. This review examines many of the scientific and technical aspects involved in using immobilized microbial cells in environmental applications, with a particular focus on cells encapsulated in biopolymer gels. Some advantages and limitations of using immobilized cells in bioreactor studies are also discussed.

Environmental applications of immobilized microbial cells: A review

Enhanced phytoextraction of an agricultural Cr- and Pb-contaminated soil by bioaugmentation with siderophore-producing bacteria.

A method of inoculating wet and dry seeds with plant growth-promoting bacteria (PGPB) using alginate microbeads as a substrate and Azospirillum brasilense as the model PGPB was developed. The microbeads were produced by low pressure spraying of an alginate solution mixed with liquid bacterial culture suspended in a very rich medium through a small nozzle resulting in small-diameter droplets. These droplets, when sprayed into a slowly stirred solution of CaCl2, immediately hardened into microbeads at diameters ranging between 100 and 200 µm. Although the process killed part of the entrapped bacteria, the remaining bacteria residing in the microbeads were sufficient [>1011 colony-forming units (CFU) g–1 inoculant] for seed inoculation. Further, it was found that the bacterial population in the inoculant could be enhanced by secondary multiplication in the same medium for an additional 16 h. It was found that the microbeads could be used either wet or dry. Dry inoculant was produced using dry air at 38°C, creating a powdery substance loaded with >109 CFU g–1 beads. Alternatively, dry microbeads were produced using a standard freeze-drying procedure. This dry preparation was easily attached to dry seed surfaces with the addition of 1% alcohol-diluted lecithin or with 0.5% synthetic paper adhesive (Resistol). The bacteria were slowly released from the microbeads in amounts ranging from 104 to 106 CFU g–1 depending on the type (wet or dry, with or without skim milk) and the time of incubation (the longer the incubation period, the smaller the amount of bacteria released with time). The wet and dry inoculants enhanced the development of wheat and tomato seedlings growing in unfertile soil, and biodegraded within 15 days in moist soil.

/pdf/alginate-microbeads-as-inoculant-carriers-for-plant-growth-3ioregmgk9.pdf

Alginate microbeads as inoculant carriers for plant growth-promoting bacteria

The survival of Pseudomonas fluorescens cells encapsulated in alginate beads and colonization of wheat roots was studied in soil microcosms inoculated with the cells in alginate beads of varying composition. Cells encapsulated in beads and introduced into a non-sterile loamy sand survived better than cells added directly to the same soil. A recovery/growth step for the bead-encapsulated cells was added before they were introduced into the soil, in an attempt to obtain optimal population levels in the soil. Further, bacterial populations that grew to the highest density in the beads subsequently showed the highest survival levels in soil. The addition of 3% skim milk, or 3% skim milk and 3% bentonite clay to all bead types consistently resulted in the highest survival of the encapsulated cells in soil. Root colonization by P. fluorescens was generally not impaired by the encapsulation in alginate. One week after inoculation into the soil, encapsulated cells in the various bead types were able to colonize the wheat rhizoplane at high population levels, similar to or exceeding those found when free cells were inoculated. In a second root colonization experiment the wheat rhizoplane was also efficiently colonized 7 weeks after the inoculant cells had been introduced into the soil in different bead types. In both assays, the cells encapsulated in beads amended with skim milk plus bentonite clay showed the highest root colonization rates. It is clear, therefore, that alginate-mediated establishment of inoculants can improve inoculant effectiveness.

Survival of, and root colonization by, alginate-encapsulated Pseudomonas fluorescens cells following introduction into soil

Handle everyday research tasks with reliable, citation-backed results

Your personal Research Agent to handle research tasks with citation-backed results

Popular Tasks used by Researchers

How can I help with your research?

Meet SciSpace

Get more enhanced response by uploading the PDFs you want me to reference.

No relevant PDFs in your library

SciSpace is the AI research assistant for academics. Run systematic literature reviews on 280M+ papers, and write papers with cited sources. Trusted by 1M+ students, PhDs & researchers.

SciSpace | AI for Research

Analyze PDFs

Code & Manuscripts

Funding & Grants

Literature & Patents

Medical & Clinical Data

Systematic Review

Visualize & Present

Web & Data

Build a Google Scholar-like website for your research.

Build a website

Create charts and images for your research

Create a Chart

Write a paper for submission to a journal

Draft a manuscript

Patent Search

Design eye-catching scientific posters in minutes.

Scientific Poster Generation

Systematic Literature Review

One task is running at the moment. Your messages will be shown right after.

Drag and drop or click here to browse

Loved by <highlight>1 million+</highlight> researchers

Extract a list of specific topics and their sources from unstructured text

Topics

Compare and analyze relevant papers that matches with your search

Papers

Get insights from PDFs and bookmarked papers from your library

My library

Recent searches

Try searching for:

Catch AI-generated content in scholarly and non-scholarly content

{ai} Detector

Ai Writer

Get PDF Summaries, highlighted text explanations 

Chat with PDF

Effortlessly create in-text citations and bibliographies in APA and 2,500 other formats

Citation generator

Get explanations, summaries, and answers on academic papers

Ease up your research workflow with {scispace}'s cohort of exciting AI tools

Elevate your academic writing skills and convey your ideas the way you want

Paraphraser

Explore our range of reading and writing tools

Your file is being prepared and should be ready in a few minutes. If it's a large file, it might take a bit longer. You can close this window, and we'll email you the file when it's done.

You have reached a maximum limit of <strong>{limit}</strong> columns in the table. Remove at least <strong>1</strong> column to add or create another one.

D. Jain

Author Tools

Chat about Author

Papers

Survival of, and root colonization by, alginate-encapsulated Pseudomonas fluorescens cells following introduction into soil