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Physiology of Moss-Bacterial Associations
Published in R. N. Chopra, Satish C. Bhatla, Bryophyte Development: Physiology and Biochemistry, 2019
Luretta D. Spiess, Barbara B. Lippincott, James A. Lippincott
Competition between different rhizosphere bacteria can also influence plant growth response, either directly by the production of growth-promoting products or indirectly by the inhibition of harmful organisms.11 Roots may be colonized by a variety of bacteria that hinder root growth. Toxigenic but nonparasitic species of Pseudomonas, Enterobacter, Klebsiella, Citrobacter, Flavobacterium, Achromobacter, and Arthrobacter groups have been described.19 Reversal of the effects of these bacteria on sugar beets by plant-growth-promoting rhizobacteria was demonstrated in greenhouse experiments.5 Other organisms may protect against these deleterious effects by forming antibiotics or siderophores (high-affinity iron transport compounds), by physically displacing harmful bacteria, or by producing growth-promoting substances. About 8 to 15% of bacteria in the rhizosphere have been found to be harmful, while only 2 to 5% promote growth. Most of these beneficial bacteria produce broad-spectrum antibiotics in vitro.20 However, there seems to be little correlation between the ability of these microorganisms to exhibit antibiosis in agar plate tests and their capacity to control pests in the field.20 The contribution of these substances to the beneficial effects of these bacteria still has to be clearly demonstrated.
Insight into Knapsack Metabolite Ecology Database: A Comprehensive Source of Species: Voc-Biological Activity Relationships
Published in Raquel Cumeras, Xavier Correig, Volatile organic compound analysis in biomedical diagnosis applications, 2018
Azian Azamimi Abdullah, M.D. Altaf-Ul-Amin, Shigehiko Kanaya
Conventional agricultural industry relies on a wide use of chemical pesticides and fertilizers. However, increased demand for organic products shows that consumers prefer reduced chemical use. Therefore, a novel sustainable agriculture needs to be developed for crop protection and prevention from using harmful chemicals. VOCs emitted by bacteria and fungi might have the potential as an alternative to the use of chemical pesticides to protect plants from pests and pathogens (Kanchiswamy et al., 2015a). It is because VOCs released by some rhizobacteria can enhance plant growth as well as inhibit the growth of other microorganisms. For example, acetoin and 2,3-butanediol released by rhizobacteria were found to promote the growth of Arabidopsis thaliana seedlings (Kai et al., 2016). A number of frequently emitted VOCs such as hexanal and 2-E-hexenal show antifungal activity and have been developed as an alternative to synthetic chemicals (Ayseli and Ayseli, 2016). Chemical ecologists also consider microbial VOCs as potential signaling molecules or semiochemicals that function as attractants and repellents to insects and other invertebrates. Pheromone traps are VOC based equipment for controlling pests without using harmful pesticides. In this strategy, pest insects may be diverted away from high-value crops using attractants, while simultaneously being repelled from high-value crops with repellents. Furthermore, natural enemies of insect pests, which are predators and parasitoids, may be simultaneously attracted making the use of semiochemicals a much more viable integrated management strategy than broad-spectrum chemical insecticides. For agriculture scientists, microbial VOCs are seen as biocontrol agents to control various phytopathogens and as biofertilizers for plant growth promotion (Kanchiswamy et al., 2015b). These examples indicate that the VOCs might have a potential impact on crop welfare and sustainable agriculture.
Rhizobacterial biofilm and plant growth promoting trait enhancement by organic acids and sugars
Published in Biofouling, 2020
Jishma Panichikkal, Radhakrishnan Edayileveetil Krishnankutty
Chemotaxis of plant growth promoting rhizobacteria (PGPR) towards the rhizosphere is an important rudiment of rhizobacterial interaction with plants as it leads to colonization and biofilm formation on the root surface. Biofilms have unique characteristics that are different from planktonic cells. The successful establishment of PGPR biofilms on the root surfaces could be considered to be governed by various factors including plant hormones, the components of root exudates, other soil microbiome, soil organic matter, moisture content, pH, soil type and climatic conditions (Backer et al. 2018). Although the components of root exudates, especially the sugars and organic acids, are considered to play a key role in biofilm formation and activation of the beneficial traits of PGPR, detailed insights into this process have not been reported.
Nanotoxicity of engineered nanomaterials (ENMs) to environmentally relevant beneficial soil bacteria – a critical review
Published in Nanotoxicology, 2019
Ricky W. Lewis, Paul M. Bertsch, David H. McNear
Much of the research on the environmental toxicology of ENMs has focused on aquatic organisms (Klaine et al. 2008; Maurer-Jones et al. 2013); however, material flow analysis and risk evaluation suggests a majority of ENMs will ultimately be deposited in soils via the wastewater treatment-biosolid-land application pathway (Gottschalk et al. 2009; Judy and Bertsch 2014). There is growing interest in the study of ENM behavior in terrestrial systems, but the complexities of working with nanoscale materials (i.e. system-induced particle transformation) in complex media, such as soil, have posed significant challenges (Dinesh et al. 2012; Pan and Xing 2012; Judy and Bertsch 2014; Djurišić et al. 2015). Soil micro-organisms are the primary drivers for delivering ecosystem services in soil, including nutrient and carbon cycling as well as immobilization, degradation, and detoxification of contaminants, leading to overall maintenance of soil health (Torsvik and Øvreås 2002; Nannipieri et al. 2003; Saccá et al. 2017). An important subset of bacteria found to directly and indirectly promote plant growth is known as plant growth-promoting rhizobacteria (PGPR). PGPR play key roles related to plant health, including plant protective responses to pathogens, drought tolerance, and nutrient acquisition (Dardanelli et al. 2010; Vejan et al. 2016; Etesami and Maheshwari 2018; Shameer and Prasad 2018).