Soil Disinfestation: From Soil Treatment to Soil and Plant Health.

This feature article tracks 100 years of soil disinfestation, from the goal of eradicating soilborne pathogens and pests to much milder approaches, aimed at establishing a healthier soil, by favoring or enhancing the beneficial soil microflora and introducing biological control agents. Restrictions on the use of many chemical fumigants is favoring the adoption of nonchemical strategies, from soilless cultivation to the use of physical or biological control measures, with more focus on maintaining soil microbial diversity, thus enhancing soil and plant health. Such approaches are described and discussed, with special focus on their integrated use.

Growth interferences between bacterial strains from raw cow's milk and their impact on growth of Listeria monocytogenes and Staphylococcus aureus.

AIMS: The purpose of this study was to detect growth enhancing or inhibiting activity between bacterial populations from raw milk under different conditions (temperature, medium). METHODS AND RESULTS: The interference of 24 raw milk isolates on growth of each other and on Listeria monocytogenes, Staphylococcus aureus, Bacillus subtilis and Micrococcus luteus was screened by drop assay and for selected pairs in co-cultivation experiments. By drop assay, antibacterial activity was observed for 40% of the strains. About 30% of the strains showed growth-enhancing activity on other strains. Most of the isolates were well adapted to cold temperatures and showed consistent or even increased inhibiting or enhancing effects on growth of other strains at 10°C. The growth of L. monocytogenes DSM 20600T and S. aureus DSM 1104T was significantly (P < 0·05) reduced in co-cultivation with Pseudomonas protegens JZ R-192. CONCLUSIONS: Growth interferences between bacterial populations have an impact on the structure of raw milk microbiota, especially when it develops under cold storage, and it may have an effect on the prevalence of certain foodborne pathogens. SIGNIFICANCE AND IMPACT OF THE STUDY: This study demonstrates growth-inhibiting and also growth-enhancing interactions between raw milk bacteria, which must be considered when predicting bacterial growth and spoilage in food. A Ps. protegens strain isolated from raw milk showed an antagonistic effect on growth of L. monocytogenes in refrigerated raw milk.

Continuous Adaptive Evolution of a Fast-Growing Corynebacterium glutamicum Strain Independent of Protocatechuate.

Corynebacterium glutamicum is a commonly applied host for the industrial production of amino acids. While valued for its robustness, it is somewhat inferior to competing strains such as Escherichia coli because of the relatively low growth rate of 0.40 h-1 in synthetic, industrial media. Accordingly, adaptive laboratory evolution (ALE) experiments were performed in continuous cultivation mode to select for a growth-improved host. To ensure industrial attractiveness, this ALE study aimed at a reduction of dependency on costly growth-boosting additives such as protocatechuate (PCA) or complex media supplements. Consequently, double selection pressures were installed consisting of a steady increase in growth rate demands and a parallel reduction of complex medium fractions. Selection yielded C. glutamicum EVO5 achieving 0.54 h-1 and 1.03 gGlc gCDW -1 h-1 in minimal medium without abovementioned supplements. Sequencing revealed 10 prominent mutations, three of them in key regulator genes.

Functional analyses of NDPK2 in Populus trichocarpa and overexpression of PtNDPK2 enhances growth and tolerance to abiotic stresses in transgenic poplar.

Nucleoside diphosphate kinases (NDPKs) are multifunctional proteins that regulate a variety of eukaryotic cellular activities, including cell proliferation, development, and differentiation. NDPK2 regulates the expression of antioxidant genes in plants. In a previous study, the Arabidopsis thaliana NDPK2 gene (AtNDPK2) was found to be associated with H2O2-mediated mitogen-activated protein kinase signaling in Arabidopsis thaliana. Proteins from transgenic plants overexpressing AtNDPK2 showed higher levels of autophosphorylation and NDPK activity and lower levels of reactive oxygen species (ROS) than those of wild-type (WT) plants. Therefore, constitutive overexpression of AtNDPK2 in Arabidopsis plants conferred enhanced tolerance to multiple environmental stresses that elicit ROS accumulation in situ. In this study, we cloned the Populus trichocarpa NDPK2 gene and analyzed its molecular structure and function. We generated and evaluated transgenic poplar plants expressing the PtNDPK2 gene under the control of the 35S promoter to achieve enhanced tolerance to various abiotic stresses. Transgenic poplar plants showed enhanced tolerance to salt and drought stress at the whole-plant level. The transgenic poplar plants showed significantly greater tolerance to 200 mM NaCl and drought stresses than WT poplar plants. In addition, the transgenic plants exhibited better growth due to increased expression of auxin-related indole acetic acid genes under normal growth conditions compared with WT plants. Our results suggest that induction of PtNDPK2 overexpression in poplars will be useful for increasing biomass production in the presence of various abiotic stresses.

Synechocystis PCC 6803 overexpressing RuBisCO grow faster with increased photosynthesis.

The ribulose-1,5-bisphosphate (RuBP) oxygenation reaction catalyzed by Ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) is competing with carboxylation, being negative for both energy and carbon balances in photoautotrophic organisms. This makes RuBisCO one of the bottlenecks for oxygenic photosynthesis and carbon fixation. In this study, RuBisCO was overexpressed in the unicellular cyanobacterium Synechocystis PCC 6803. Relative RuBisCO levels in the engineered strains FL50 and FL52 increased 2.1 times and 1.4 times, respectively, and both strains showed increased growth, photosynthesis and in vitro RuBisCO activity. The oxygen evolution rate increased by 54% and 42% on per chlorophyll basis, while the in vitro RuBisCO activity increased by 52% and 8.6%, respectively. The overexpressed RuBisCO were tagged with a FLAG tag, in strain FL50 on the N terminus of the large subunit while in strain FL52 on the C terminus of the small subunit. The presence of a FLAG tag enhanced transcription of the genes encoding RuBisCO, and, with high possibility, also enhanced the initiation of translation or stability of the enzyme. However, when using a streptavidin-binding tag II (strep-tag II), we did not observe a similar effect. Tagged RuBisCO offers an opportunity for further studying RuBisCO expression and stability. Increased levels of RuBisCO can further improve photosynthesis and growth in the cyanobacterium Synechocystis PCC 6803 under certain growth conditions.