Water activity, temperature, and pH effects on growth of the biocontrol agentPantoea agglomeransCPA-2

2002 ◽  
Vol 48 (12) ◽  
pp. 1082-1088 ◽  
Author(s):  
E Costa ◽  
J Usall ◽  
N Teixidó ◽  
J Delgado ◽  
I Viñas
Keyword(s):  
Water Activity ◽  
Bacterial Growth ◽  
Biocontrol Agent ◽  
Great Influence ◽  
Ph Effects ◽  
Sucrose Medium ◽  
Activity Temperature ◽  
Ph Conditions ◽  
Yeast Extract Sucrose

The growth response of the biocontrol agent Pantoea agglomerans to changes in water activity (aw), temperature, and pH was determined in vitro in nutrient yeast extract-sucrose medium. The minimum temperature at which P. agglomerans was able to grow was 267–272 kelvins (–6 to –1°C), and growth of P. agglomerans did not change at varying pH levels (4.5–8.6). The minimum awfor growth was 0.96 in media modified with glycerol and 0.95 in media modified with NaCl or glucose. Solute used to reduce water activity had a great influence on bacterial growth, especially at unfavourable conditions (e.g., low pH or temperature). NaCl stimulated bacterial growth under optimum temperatures but inhibited it under unfavourable pH conditions (4.5 or 8.6). In contrast, the presence of glucose in the medium allowed P. agglomerans to grow over a broad range of temperature (3–42°C) or pH (5–8.6) regimes. This study has defined the range of environmental conditions (aw, pH, and temperature) over which the bacteria may be developed for biological control of postharvest diseases.Key words: biocontrol, ecophysiology response, stress.

Water activity, temperature, and pH effects on growth of Fusarium moniliforme and Fusarium proliferatum isolates from maize

1995 ◽  
Vol 41 (12) ◽  
pp. 1063-1070 ◽  
Author(s):  
Sonia Marin ◽  
Vicente Sanchis ◽  
Naresh Magan
Keyword(s):  
Water Activity ◽  
Fusarium Moniliforme ◽  
Potential Temperature ◽  
Fusarium Proliferatum ◽  
Ph Effects ◽  
Optimum Ph ◽  
Effects Of Ph ◽  
Activity Temperature ◽  
Optimum Ph And Temperature

The effects of water activity (aw, 0.994–0.90 ≡ 0.4–14.0 (–)MPa water potential), temperature (4–45 °C), and pH (3.6, 5.5, 7.0), and their interactions on growth of isolates of Fusarium moniliforme and Fusarium proliferatum were determined in vitro on a maize extract agar medium. Growth of two isolates of F. moniliforme and four isolates of F. proliferatum were significantly influenced by water activity regardless of solute type used (NaCl, glycerol, or glucose). However, at steady-state aw levels, growth was optimum at 0.994–0.98 aw and reduced significantly at 0.92 aw. Further detailed studies with one isolate of F. moniliforme (25N) and two isolates of F. proliferatum (73N, 13 IN) showed that growth occurred over the range of 0.994–0.90 aw in the temperature range 20–35 °C with slight differences between species. Growth did occur at 4 °C and 0.994–0.96 aw, but no growth was recorded at 40 and 45 °C regardless of aw. Profiles of aw × temperature relations for growth of these two species were constructed from these data for the first time. Optimum pH and temperature for growth was 5.5 and 25 °C for both isolates of F. proliferatum, and pH 7.0 and 30 °C for the isolate of F. moniliforme. However, for the latter isolate at <0.98 aw, optimum pH and temperature for growth changed. The effects of pH, temperature, and aw for single, two-way and three-way interactions were all found to be statistically significant for these three isolates. The ecological significance of this information for understanding these important fumonisin-producing fungi is discussed.Key words: water activity, temperature, fumonisin-producing, Fusarium moniliforme, Fusarium proliferatum, maize.

Water and temperature relations and microconidial germination of Fusarium moniliforme and Fusarium proliferatum from maize

1996 ◽  
Vol 42 (10) ◽  
pp. 1045-1050 ◽  
Author(s):  
Sonia Marín ◽  
V. Sanchis ◽  
A. Teixido ◽  
R. Saenz ◽  
A. J. Ramos ◽  
...  
Keyword(s):  
Water Activity ◽  
Fusarium Moniliforme ◽  
Potential Temperature ◽  
Gompertz Model ◽  
Linear Increase ◽  
Fusarium Proliferatum ◽  
Activity Temperature ◽  
Lag Times ◽  
Lag Phases

The effects of water activity (aw, 0.994–0.85 = 0.4–21.0 (−)MPa water potential), temperature (5–42 °C), and their interactions on microconidial germination of three isolates each of Fusarium moniliforme and Fusarium proliferatum were determined in vitro on a maize meal extract medium. Temporal germination rates of microconidia of isolates of both species were significantly influenced by both aw and temperature. Germination was very rapid at >0.94 aw with an almost linear increase with time. Germination rates of microconidia of F. moniliforme were slower than those of F. proliferatum isolates at marginal aw levels and 5–25 °C, while at higher temperature (30–37 °C), the former germinated more rapidly than the latter. The aw minima for germination of isolates of both species was 0.88, with none occurring at 0.85 aw over a 40-day incubation period. At 37 °C, isolates of F. moniliforme had slightly lower aw minima than those of F. proliferatum. The narrowest range of aw for germination was at 5 °C, and none occurred at 42 °C. The effect of aw × temperature interactions on the lag phases (h) prior to germination and the germination rates (h−1) were estimated using the Gompertz model and the Zwietering equation. This showed that lag phases were shorter at 25–30 °C and 0.994–0.98 aw, and were increased to 10–500 h at marginal temperatures (5–10 °C) for F. proliferatum and longer for F. moniliforme. At marginal aw levels (0.92–0.90), lag times were increased to >250 h. Germination rates (h−1) were different for the two species. Microconidia of F. moniliforme germinated optimally at 25–37 °C and 0.96–0.98 aw, but this changed to 30 °C at 0.90–0.94 aw, while germination of microconidia of F. proliferatum remained optimum at 30 °C, regardless of aw. There were statistically significant (P < 0.01) effects of aw, temperature, isolate, and two- and three-way interactions for F. proliferatum, but there were no intraisolate effects for F. moniliforme. The ecological significance of these data for understanding colonization patterns of these important fumonisin-producing fungi are discussed.Key words: water activity, temperature, germination, fumonisin producing, Fusarium spp.

Effect of the endophytic plant growth promoting Enterobacter ludwigii EB4B on tomato growth

2020 ◽  
Vol 13 (2) ◽  
pp. 54-65 ◽  
Author(s):  
M.E.A. Bendaha ◽  
H.A. Belaouni
Keyword(s):  
Root Length ◽  
Biocontrol Agent ◽  
Growth Promotion ◽  
Dry Weight ◽  
Antagonistic Activity ◽  
Rrna Gene ◽  
Plant Growth Promoting ◽  
Enterobacter Ludwigii ◽  
Tomato Growth

SummaryThis study aims to develop a biocontrol agent against Fusarium oxysporum f.sp. radicis-lycopersici (FORL) in tomato. For this, a set of 23 bacterial endophytic isolates has been screened for their ability to inhibit in vitro the growth of FORL using the dual plate assay. Three isolates with the most sound antagonistic activity to FORL have been qualitatively screened for siderophore production, phosphates solubilization and indolic acetic acid (IAA) synthesis as growth promotion traits. Antagonistic values of the three candidates against FORL were respectively: 51.51 % (EB4B), 51.18 % (EB22K) and 41.40 % (EB2A). Based on 16S rRNA gene sequence analysis, the isolates EB4B and EB22K were closely related to Enterobacter ludwigii EN-119, while the strain EB2A has been assigned to Leclercia adecarboxylata NBRC 102595. The promotion of tomato growth has been assessed in vitro using the strains EB2A, EB4B and EB22K in presence of the phytopathogen FORL. The treatments with the selected isolates increased significantly the root length and dry weight. Best results were observed in isolate EB4B in terms of growth promotion in the absence of FORL, improving 326.60 % of the root length and 142.70 % of plant dry weight if compared with untreated controls. In the presence of FORL, the strain EB4B improved both root length (180.81 %) and plant dry weight (202.15 %). These results encourage further characterization of the observed beneficial effect of Enterobacter sp. EB4B for a possible use as biofertilizer and biocontrol agent against FORL.

Effect of C6-Volatiles on Bioluminescent Plant Pathogens

HortScience ◽  
1998 ◽  
Vol 33 (3) ◽  
pp. 557d-557
Author(s):  
Jennifer Warr ◽  
Fenny Dane ◽  
Bob Ebel
Keyword(s):  
Biological Activity ◽  
Bacterial Growth ◽  
Xanthomonas Campestris ◽  
Plant Pathogens ◽  
Genetically Engineered ◽  
The Other ◽  
Computer Assisted ◽  
Signal Molecules ◽  
Low Concentrations

C6 volatile compounds are known to be produced by the plant upon pathogen attack or other stress-related events. The biological activity of many of these substances is poorly understood, but some might produce signal molecules important in host–pathogen interactions. In this research we explored the possibility that lipid-derived C6 volatiles have a direct effect on bacterial plant pathogens. To this purpose we used a unique tool, a bacterium genetically engineered to bioluminesce. Light-producing genes from a fish-associated bacterium were introduced into Xanthomonas campestris pv. campestris, enabling nondestructive detection of bacteria in vitro and in the plant with special computer-assisted camera equipment. The effects of different C6 volatiles (trans-2 hexanal, trans-2 hexen-1-ol and cis-3 hexenol) on growth of bioluminescent Xanthomonas campestris were investigated. Different volatile concentrations were used. Treatment with trans-2 hexanal appeared bactericidal at low concentrations (1% and 10%), while treatments with the other volatiles were not inhibitive to bacterial growth. The implications of these results with respect to practical use of trans-2 hexanal in pathogen susceptible and resistant plants will be discussed.

scholarly journals Influence of nutrient availability on in vitro growth of major bovine mastitis pathogens

2021 ◽  
Vol 88 (1) ◽  
pp. 80-88
Author(s):  
Remo Stürmlin ◽  
Josef J. Gross ◽  
Olga Wellnitz ◽  
Lea A. Wagner ◽  
Camille Monney ◽  
...  
Keyword(s):  
Bacterial Growth ◽  
Nutrient Availability ◽  
Bovine Mastitis ◽  
Milk Composition ◽  
B Vitamins ◽  
E Coli ◽  
Streptococcus Uberis ◽  
Whole Milk ◽  
Mastitis Pathogens

AbstractThe aim of the present study was to investigate the effects of milk composition changes on the in vitro growth of bovine mastitis pathogens. Nutritional requirements of three major bovine mastitis pathogens Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), and Streptococcus uberis (S. uberis) were investigated in vitro. We used ultra-high temperature (UHT) treated milk with different contents of fat, protein, and carbohydrates to test the influence of the availability of various milk constituents on pathogen growth characteristics. Additionally, the bacterial growth was investigated under experimentally modified nutrient availability by dilution and subsequent supplementation with individual nutrients (carbohydrates, different nitrogen sources, minerals, and different types of B vitamins) either to milk or to a conventional medium (thioglycolate broth, TB). Varying contents of fat, protein or lactose did not affect bacterial growth with the exception of growth of S. uberis being promoted in protein-enriched milk. The addition of nutrients to diluted whole milk and TB partly revealed different effects, indicating that there are media-specific growth limiting factors after dilution. Supplementation of minerals to diluted milk did not affect growth rates of all studied bacteria. Bacterial growth in diluted whole milk was decreased by the addition of high concentrations of amino acids in S. aureus, and by urea and additional B vitamins in E. coli and S. aureus. The growth rate of S. uberis was increased by the addition of B vitamins to diluted whole milk. The present results demonstrate that growth-limiting nutrients differ among pathogen types. Because reduced bacterial growth was only shown in diluted milk or TB, it is unlikely that alterations in nutrient availability occurring as a consequence of physiological changes of milk composition in the cow's udder would directly affect the susceptibility or course of bovine mastitis.

scholarly journals Evaluation of Indigenous Olive Biocontrol Rhizobacteria as Protectants against Drought and Salt Stress

2021 ◽  
Vol 9 (6) ◽  
pp. 1209
Author(s):  
Nuria Montes-Osuna ◽  
Carmen Gómez-Lama Cabanás ◽  
Antonio Valverde-Corredor ◽  
Garikoitz Legarda ◽  
Pilar Prieto ◽  
...  
Keyword(s):  
Salt Stress ◽  
Abiotic Stresses ◽  
Biochemical Parameters ◽  
Biocontrol Agent ◽  
Negative Effects ◽  
Experimental Conditions ◽  
Acds Gene ◽  
Drought And Salt Stress ◽  
Physiological And Biochemical

Stress caused by drought and salinity may compromise growth and productivity of olive (Olea europaea L.) tree crops. Several studies have reported the use of beneficial rhizobacteria to alleviate symptoms produced by these stresses, which is attributed in some cases to the activity of 1-aminocyclopropane-1-carboxylic acid deaminase (ACD). A collection of beneficial olive rhizobacteria was in vitro screened for ACD activity. Pseudomonas sp. PICF6 displayed this phenotype and sequencing of its genome confirmed the presence of an acdS gene. In contrast, the well-known root endophyte and biocontrol agent Pseudomonas simiae PICF7 was defective in ACD activity, even though the presence of an ACD-coding gene was earlier predicted in its genome. In this study, an unidentified deaminase was confirmed instead. Greenhouse experiments with olive ‘Picual’ plants inoculated either with PICF6 or PICF7, or co-inoculated with both strains, and subjected to drought or salt stress were carried out. Several physiological and biochemical parameters increased in stressed plants (i.e., stomatal conductance and flavonoids content), regardless of whether or not they were previously bacterized. Results showed that neither PICF6 (ACD positive) nor PICF7 (ACD negative) lessened the negative effects caused by the abiotic stresses tested, at least under our experimental conditions.

scholarly journals Evaluation of Starch Hydrolysis for Glycemic Index Prediction of Rice Varieties

Proceedings ◽  
2020 ◽  
Vol 70 (1) ◽  
pp. 101
Author(s):  
Cristiana Pereira ◽  
Regina Menezes ◽  
Vanda Lourenço ◽  
Teresa Serra ◽  
Carla Brites
Keyword(s):  
Glycemic Index ◽  
Food Processing ◽  
Amylose Content ◽  
Rice Variety ◽  
Great Influence ◽  
Starch Hydrolysis ◽  
Rice Starch ◽  
Rice Varieties ◽  
Processing Technologies

Rice consumed as white cooked polished grain has been considered a high glycemic index (GI) food, particularly compared with other starchy foods. However, the GI levels of rice based food can vary among different rice types and food processing technologies. Rice GI variation can be affected by several factors, such as rice variety, the genetic background of rice as well as due to crop edaphoclimatic conditions. The main difference in rice starch composition that influences GI is the amylose content. Besides the chemical composition of rice, the gelatinization characteristics and food processing can also contribute to starch retrogradation, thus increasing the level of resistant starch with a great influence on GI. To understand the glycemic response of rice types differing in amylose and viscosity profiles, four rice samples were analyzed and compared with standard and resistant HI-MAIZE corn starches. An in vitro enzymatic starch hydrolysis procedure was applied to estimate GI. The results indicate substantial differences in the starch hydrolysis of the two corn starches. Starch hydrolysis tended to be more rapid and efficient for ‘Waxy’ and ‘Ceres’ (intermediate-amylose) rice types than for ‘Maçarico’ (high-amylose rice). In addition, the data show that the Maçarico variety has the lowest estimated GI and the highest retrogradation rate compared with ‘Waxy’, ‘Ceres’ and ‘Basmati’ type. The results obtained reinforce the importance of knowing amylose content and viscosity profiles for the prediction of rice glycemic responses.

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