Comparative laboratory studies on three fungal pathogens of the elm bark beetle Scolytus scolytus: Effect of temperature and humidity on infection by Beauveria bassiana,Metarhizium anisopliae, and Paecilomyces farinosus

Larvae of the elm bark beetle, Scolytus scolytus, were inoculated with conidia of the entomogenous fungi Beauveria bassiana (two strains), Metarhizium anisopliae (two strains), and Paecilomyces farinosus (two strains) and incubated over a range of temperatures (2°, 6°, 10°, 15°, and 20°C). One strain each of B. bassiana and P. farinosus caused infection even at 2°C, whereas the two strains of M. anisopliae caused no infection below 10°C. Infection of adult beetles by B. bassiana (one strain) and M. anisopliae (one strain) was tested at 15°, 20°, and 25°C (B. bassiana) and at 15° and 20°C (M. anisopliae). Fungal infection occurred at all three temperatures, but at 25°C beetles tended to succumb to bacterial infection. The effect of relative humidity on infection of larvae by B. bassiana (one strain), M. anisopliae (one strain), and P. farinosus (one strain) was tested at 51, 74, 86, 90, 95, 97.5, and 100% relative humidity. B. bassiana and M. anisopliae caused some infection at all humidities: with P. farinosus there was no infection at the two lowest humidities. Mortality due to infection by these fungi was most rapid at the highest humidities.     

Mortality of bifidobacteria in boiled yogurt

Bifidobacterial strains showed various mortalities during storage at 30°C in boiled yogurt prepared with Streptococcus sp. and Lactobacillus sp. Bifidobacterium breve 203 was most stable, maintaining its initial cell number for more than 5 days. It was also stable at 4 or 10°C in fresh yogurt. B. longum 401 rapidly lost viability in the boiled yogurt and was unstable in the fresh yogurt at any temperature. Lactobacillus sp. remained fully viable for one week or more at 4–30°C while Streptococcus sp. lost viability at 20°C or above. The difference in mortality between B. breve 203 and B. longum 401 was mainly due to their sensitivity to the acidic environment, with temperature during storage having a secondary effect. Effects of lysozyme, pepsin and bile acids on the two strains were also investigated.     

Desiccation tolerance of Botryococcus braunii (Trebouxiophyceae,Chlorophyta) and extreme temperature tolerance of dehydrated cells

Botryococcus braunii Kützing, a green colonial microalga, occurs worldwide in both freshwater and brackish water environments. Despite considerable attention to B. braunii as a potential source of renewable fuel, many ecophysiological properties of this alga remain unknown. Here, we examined the desiccation and temperature tolerances of B. braunii using two newly isolated strains BOD-NG17 and BOD-GJ2. Both strains survived through 6- and 8-month desiccation treatments but not through a 12-month treatment. Interestingly, the desiccation-treated cells of B. braunii gained tolerance to extreme temperature shifts, i.e., high temperature (40 °C) and freezing (?20 °C). Both strains survived for at least 4 and 10 days at 40 and ?20 °C, respectively, while the untreated cells barely survived at these temperatures. These traits would enable long-distance dispersal of B. braunii cells and may account for the worldwide distribution of this algal species. Extracellular substances such as polysaccharides and hydrocarbons seem to confer the desiccation tolerance.     

Potential of patulin production by Penicillium expansum strains on various fruits

In this study, we investigated the pathogenicity and patulin production by ten strains of Penicillium expansum on various fruits (apples, apricots, kiwis, plums and peaches) at two (4°C and 25°C) different temperature regimes. All strains caused the infectious rots on all fruits at 4 and 25°C except one strain (PEX 09) at 4°C. Two strains (PEX 20 and PEX 12) out of ten produced the highest amounts of patulin on all fruits tested. The patulin production by P. expansum is high at 25°C compared to 4°C. All strains of P. expansum accumulated patulin ranging from 100–13,200 μg/kg and nine strains ranging from 100–12,100 μg/kg in all fruits at 25°C and 4°C, respectively. Among ten strains of P. expansum, strain PEX 20 produced the greatest amount of patulin on apricots (13,200 μg/kg of rotten fruit) and on apples (12,500 μg/kg) at 25°C after 9 days of incubation. At 4°C, this strain produced 12,100, 12,000, 2,100 and 1,200 μg/kg of patulin on apricots, apples, plums and peaches, respectively, after 45 days of incubation. Strain PEX 12 produced the highest amount of patulin on kiwis (10,700 μg/kg) at 25°C and 10,300 μg/kg at 4°C. Patulin production by P. expansum on peaches and plums at both temperatures were lower than other fruits. The results of this study showed that careful removal of rotten fruits is essential to produce patulin-free fruit juice, since high patulin levels in apricots, apples and kiwis could result in a level greater than 50 μg/kg of this mycotoxin in finished fruit juices, when one contaminated fruit occurs in 264, 250 and 214 fruits, respectively. So, the fruit processors should take care in not using rotten fruits for juice production to avoid the patulin problem worldwide, since this study proved that most important fruits being used for juice production and direct human consumption are susceptible to P. expansum and subsequent patulin production even at low temperatures. This is the first comprehensive report regarding patulin production by different strains of P. expansum on various fruits from Italy at different temperature regimes.     

The growth of four species of Azolla as affected by temperature

The growth of 22 strains of Azolla pinnata R. Br., 3 strains of A. filiculoides Lam. and one strain each of A. mexicana Presl and A. caroliniana Willd. was tested separately in liquid culture media kept in controlled, artificial light (30 klux) growth cabinets. Three temperature levels were used: 33°C (37/29°C day/night), 29°C (33/25°C) and 22°C (26/18°C)/ Photoperiod was 12 h a day.For most A. pinnata strains (except three) and an A. mexicana strain the maximum weekly relative growth rate was higher at 33°C than at 22°C, but not for A. filiculoides and A. caroliniana. The highest value of maximum relative growth rate corresponded to 1.9 doubling days and in most strains this occurred in the first week. As the plants grew, the growth rate slowed down more severely at higher temperatures. The maximum biomass was higher at 22°C than at 33°C in all strains. At 22°C, it took 30–50 days to attain maximum biomass and the highest value was 14 g N m^?2 or 320 g dry m^?2 by A. caroliniana, followed by 12 g N m^?2 or 290 g dry wt. m^?2 by one strain of A. filiculoides. At 29°C, the maximum biomass was attained in 20–35 days. The highest value was 6.3 g N m^?2 or 154 g dry wt. m^?2 by A. caroliniana. At 33°C, most A. pinnata strains gave a maximum biomass of less than 4 g N m^?2 after 13–23 days, while some strains grew up to 30 days, resulting in a higher maximum biomass. The highest maximum biomass at 33°C was 5.5 g N m^?2 or 140 g m^?2 dry wt. by A. pinnata from Cheng Mai while the maximum biomass of A. filiculoides and A. caroliniana was much less. Azolla filiculoides requires lower temperature than other species for its growth. Azolla pinnata has the best tolerance to high temperatures among the four species. Azolla mexicana could not be discriminated from A. pinnata in its response to temperature. Azolla caroliniana may keep an intermediate position between A. filiculoides and A. pinnata in temperature response.The formation of ammonia in the medium was examined and it occurred mostly under stationary growth conditions, but, at 33°C, some strains of A. pinnata and A. mexicana released or formed ammonia at 0.3–0.8 μg N ml^?1 per week during their initial exponential growth stage.     

Metarhizium spp. isolates from madagascar: Morphology and effect of high temperature on growth and infectivity to the migratory locust,Locusta migratoria

Five strains ofMetarhizium anisopliae (Metsch.) Sorokin and one strain ofMetarhizium flavoviride Gams &; Rozsypal originally isolated in Madagascar were studied. Measurements of conidia and, for the first time, also of blastospores produced in a liquid medium were used for species and variety determination. Blastospores ofM. flavoviride were more homogenous in their size than those ofM. anisopliae. Growth at high temperatures between 25° and 40°C showed that 4 isolates ofM. anisopliae grew at 36°C andM. flavoviride grew at 38°C. Using alternating day/night temperatures (8/16 h) the three strains tested could also tolerate 40°/25°C. In bioassays, fiveMetarhizium spp. isolates were tested against third and fourth instar larvae ofLocusta migratoria (L.) at two alternating day/night temperatures of 30°/25°C and 36°/25°C. In the cooler regime, all strains caused a mortality of 50% within 5.9 to 8.5 days (median lethal time), while in the 36°/25°C treatment only the thermophilicM. flavoviride and oneM. anisopliae strain isolated from a soil sample gave comparable results with median lethal times of 6.8 and 7.3 days, respectively.     

Antilisterial Activity on Poultry Meat of Amylolysin, a Bacteriocin from Bacillus amyloliquefaciens GA1

This paper describes the production, the purification and the antilisterial activity of amylolysin, a novel bacteriocin from B. amyloliquefaciens GA1. The strain genome was first analysed using PCR techniques for the presence of gene clusters that direct the synthesis of characterised bacteriocins from B. amyloliquefaciens and the closely related B. subtilis. Our results suggest that amylolysin corresponds to a novel bacteriocin. The effect of amylolysin on the growth of different isolates of Listeria monocytogenes was evaluated in poultry meat during 21 days of storage at 4 °C. A potent antilisterial effect was observed for all the indicator strains tested, demonstrating that amylolysin is a novel bacteriocin that could be used as a food preservative.     

Insect cell culture media for cultivation of new world Leishmania

Monophasic insect cell culture media were evaluated for suitability in the propagation of strains of Leishmania brasiliensis, L. mexicana and L. enriettii. Amastigotes were inoculated into Grace's, Schneider's and Mitsuhashi-Maramorosch's Media containing antibiotics and varying concentrations of fetal calf serum. After 4–7 days incubation at 27°C, promastigote yields exceeded 1 × 10⁸/rr.l in some instances in contrast to yields of approximately 2 × 10⁷/ml in blood-based media. Optimal concentrations of fetal calf serum were determined to be 15% or more for most of the strains tested.     

Thermotolerant oil-degrading bacteria isolated from soil and water of geographically distant regions

Oil-degrading bacteria were isolated from soil and water samples taken in Russia, Kazakhstan, and the Antarctic; 13 of 86 strains proved to be thermotolerant. These bacteria utilized crude oil at 45–50°C; their growth optimum (35–37°C) and range (20–53°C) differ from those of mesophilic bacteria. Thermotolerant strains were identified as representatives of the genera Rhodococcus and Gordonia. It was shown that their ability to degrade petroleum products does not differ at 24 and 45°C. The strains Rhodococcus sp. Par7 and Gordonia sp. 1D utilized 14 and 20% of the oil, respectively, in 14 days at 45°C. All of the isolated thermotolerant bacteria grew in a medium containing 3% NaCl; the medium for the strains Gordonia amicalis 1B and Gordonia sp. 1D contained up to 10% NaCl. The bacteria G. amicalis and Rhodococcus erythropolis were able to utilize crude oil and individual hydrocarbons at higher (up to 50°C) temperatures.     

Production of microsclerotia by Brazilian strains of Metarhizium spp. using submerged liquid culture fermentation

We investigated the potential production and desiccation tolerance of microsclerotia (MS) by Brazilian strains of Metarhizium anisopliae (Ma), M. acridum (Mc) and M. robertsii (Mr). These fungi were grown in a liquid medium containing 16 g carbon l^?1 with a carbon:nitrogen ratio of 50:1. One hundred milliliters cultures were grown in 250 ml Erlenmeyer flasks in a rotary incubator shaker at 28 °C and 200 rpm for 5 days. Five-day-old MS were harvested, mixed with diatomaceous earth (DE) and air-dried for 2 days at 30 °C. The air-dried MS–DE granular preparations were milled by mortar + pestle and stored in centrifuged tubes at either 26 or ?20 °C. Desiccation tolerance and conidia production were assessed for dried MS granules by measuring hyphal germination after incubation for 2 days on water agar plates at 26 °C and for conidia production following 7 days incubation. Yields of MS by all strains of Metarhizium were 6.1–7.3 × 10⁶ l^?1 after 3 days growth with maximum MS yields (0.7–1.1 × 10⁷ l^?1) after 5 days growth. No differences in biomass accumulation were observed after 3 days growth, whereas Ma-CG168 showed the highest biomass accumulation after 5 days growth. Dried MS–DE preparations of all fungal strains were equally tolerant to desiccation (≥93 % germination) and the highest conidia production was obtained by MS granules of Mc-CG423 (4 × 10⁹ conidia g^?1). All MS granules showed similar stability after storage at either 26 or ?20 °C for 3.5 months.     

Observations on the morphology and infectivity for cattle of Babesia bovis parasites in unfed Boophilus microplus larvae after incubation at various temperatures

Dalgliesh R. J. and Stewart N. P. 1979. Observations on the morphology and infectivity for cattle of Babesia bovis parasites in unfed Boophilus microplus larvae after incubation at various temperatures. International Journal for Parasitology9: 115–120. The temperature of incubation of unfed Boophilus microplus larvae infected with Babesia bovis influenced the morphology and infectivity of the Babesia within the tick. Incubation at 37°C for 1–3 days stimulated the development of parasites morphologically similar to those usually observed in fed larvae harvested from cattle; similar forms appeared more slowly in larvae incubated at 31°C or 25°C. Extracts prepared from larvae after incubation at 37°C for 3–5 days or 30°C for 8 days were consistently infective for cattle. Prior storage of larvae at 14°C for up to 28 days enhanced the development of infectivity at 37°C; infectivity could still be produced after 65 days storage at 14°C but not after 76 days. Larvae released on a host transmitted B. bovis sooner if they had been incubated at 37°C for 4 days. It was concluded that the development of B. bovis to an infective stage in B. microplus is temperature dependent and does not require the stimulus of feeding by the host.     

Effect of temperature on the phytotoxicity and cytotoxicity of Botryosphaeriaceae fungi

Botryosphaeriaceae fungi are phytopathogens and human opportunists. The influence of temperature on the phytotoxicity and cytotoxicity of culture filtrates of five Botryosphaeriaceae species was investigated. All culture filtrates of fungi grown at 25 °C were phytotoxic: symptoms were evaluated based on visual inspection of necrosis areas and on the maximum quantum yield of photosystem II, F_v/F_m. Diplodia corticola and Neofusicoccum kwambonambiense were the most phytotoxic, followed by Neofusicoccum parvum CAA704 and Botryosphaeria dothidea. Phytotoxicity dramatically decreased when strains were grown at 37 °C, except for B. dothidea. All strains, except N. parvum CAA366 and Neofusicoccum eucalyptorum, grown either at 25 °C or 37 °C, were toxic to mammalian cells; at 25 °C and at 37°C, D. corticola and B. dothidea were the most cytotoxic, respectively. Although the toxicity of B. dothidea to both cell lines and of N. kwambonambiense to Vero cells increased with temperature, the opposite was found for the other species tested. Our results suggest that temperature modulates the expression of toxic compounds that, in a scenario of a global increase of temperature, may contribute to new plant infections but also human infections, especially in the case of B. dothidea.     

Survival of Bactrocera latifrons (Diptera: Tephritidae) adults under constant and fluctuating low temperatures

Bactrocera latifrons (Hendel) is believed to have originated in Southeast Asia but has invaded Hawaii and most recently East Africa. This insect has also been recorded on Okinawa Island, the far south of Kyushu Island, Japan. To assess the overwintering ability of B. latifrons adults, survival at constant temperatures (8, 10, 12, 14, 15 °C) and under fluctuating thermal regimes (FTRs) was investigated. At 14 or 15 °C, more than 30 % of females survived for 90 days. Time required to kill 95 % of B. latifrons at 8 °C was estimated to be 13 days; at 10 °C, 29 days; and at 12 °C, 38 days for females, and 8, 17, and 24 days at the same above temperatures, respectively, for males, suggesting low cold tolerance of this species. The results show that females survive cold temperatures better than males. Under an FTR of 11 °C (22 h)/20 °C (2 h) (average 11.8 °C) survival of females drastically increased compared to that at a constant temperature of 12 °C, whereas the survival of males increased slightly. Survival under FTRs indicates that adult B. latifrons may not overwinter in the north of Tanegashima Island, located 30 km south of Kyushu Island, Japan.     

Detoxification of enterotoxigenic Bacillus cereus (JX455159) isolated from meat by a local strain of Lactobacillus plantarum (JX282192)

Raw minced meat samples (25) were randomly collected from different slaughterhouses in Dakhlia and Sharkyia Governorates, Egypt. One hundred and fifty Bacillus species related to the cereus group were isolated from the collected meat samples using Mannitol Yolk Polymyxin (MYP) agar plates. Purified bacterial cultures were then tested for their virulence factors with respect to hemolysin, protease and lecithinase. Of the tested Bacillus strains (150), 81, 95.3 and 76 % of total tested Bacillus strains were positive for hemolysin, protease and lecithinase tests, respectively. The identity of one of the most potent strains suspected and encoded as Bacillus cereus F23 was confirmed by amplifying its 16S rRNA gene. The partial nucleotide sequence of the amplified 16S rRNA gene of the tested strain was submitted to GenBank with accession number JX455159. Multiplex PCR amplification of enterotoxin genes in the tested strain, using specific primers, yielded amplicons of molecular sizes 695 and 565 bp for enterotoxins hblC and cytK, respectively. Thermal resistance of B. cereus F23 (JX455159) spores was determined by calculating D values at 65, 75, 85 and 95 °C for 36, 25, 19 and 16 min, respectively, and the calculated Z value was recorded as 0.119 °C. A lactic acid bacteria (LAB) strain isolated from pickles was preliminary identified as Lactobacillus plantarum F14 (LBF14) and later confirmed by detecting its 16S rRNA gene, and it was submitted to GenBank with accession number JX282192. The identified LAB strain was tested as a bioprotective agent against toxigenic B. cereus F23 spores both in minced meat samples and BHI broth medium. A reduction in B. cereus F23 population between 4 and 6 log cycles under different tested conditions was recorded. The activity of virulence factors (protease and lecithinase) decreased and hemolytic activity was completely inhibited in the presence of 10³ CFU/ml of Lactobacillus plantarum F14 (JX282192). Inthe presence of 10⁵ CFU/ml Lactobacillus plantarum F14 (JX282192), protease and lecithinase activities of B. cereus F23 were decreased by 85 and 71 %, respectively.     

Inhibition ofCitrobacter freundii by lactic acid, ascorbic acid, citric acid,Thymus vulgaris extract and NaCl at 31 °C and 5 °C

Citrobacter freundii has been implicated in food spoilage and food poisoning outbreaks. This study examines the effects of some compounds (e.g. citric acid, ascorbic acid, lactic acid, sodium chloride, andThymus vulgaris extract) on growth of two strains of Citrobacter freundii at 31 °C and 5 °C. At 31 °C, lactic acid (0.2%) or ascorbic acid (0.2%) alone completely inhibited growth of the tested strains, as there was 100% reduction in growth of the strains after 24 h incubation in nutrient broth containing these compounds.Thymus vulgaris extract (0.3%) reduced the growth rate (p<0.05), the percentages of inhibition after 24 h incubation were about 60% for both strains. NaCl (5%) greatly reduced growth, the percentages of inhibition were about 84% for both strains. Combination ofT. vulgaris extract (0.3%) and NaCl (4%) together completely inhibited growth ofC. freundii species tested. Ascorbic acid (0.1%) or citric acid (0.03%) did not affect growth of the strains (p>0.05), but a lag occurred before increase in number could be observed. In chicken and fish homogenates, combination of NaCl (4%) and ascorbic acid (0.1%) reduced the growth (p < 0.05) (growth inhibition was 40%). At 5 °C, lactic acid (0.1%) alone greatly reduced the growth (p<0.05). The activity of NaCl, or ascorbic acid alone against the tested strains was greatly increased (p<0.05). ForC. freundii 4, the percentage of growth inhibition after 6 days incubation in broth containing 3% NaCl or 0.1% ascorbic acid were 88% and 72%, respectively. ForC. freundii 38, the percentage of growth inhibition after 6 days incubation in broth containing these compounds were 60% and 54%, respectively.     

Cold tolerance of the coconut hispine beetle, <Emphasis Type="Italic">Brontispa longissima</Emphasis> (Coleoptera: Chrysomelidae) in Japan

The coconut hispine beetle, Brontispa longissima (Gestro), supposedly originated from Papua New Guinea and Indonesia but has recently invaded Southeast and East Asian countries where it has been causing serious damage to Cocos nucifera L. This insect also occurs on the Southwest Islands off Kyushu Island in Japan. To evaluate the potential northward range expansion of this insect in Japan, we investigated its cold tolerance at 0, 5, and 10 °C (egg, larva, pupa, and adult), 13 °C (adult), and 15 °C (egg and hatched larva). At 15 °C, few eggs hatched, and the larvae that hatched died within a few days of hatching. At 13 °C, Ltime₉₅ was estimated to be 23 days for adults, with the most cold-tolerant developmental stage at 10 °C. At all developmental stages, Ltime₉₅ of B. longissima was estimated to be 19 days at 10 °C, 8 days at 5 °C, and 5 days at 0 °C, suggesting the cold tolerance of this beetle is very low. Considering average daily temperatures, it is unlikely that B. longissima can establish itself north of Amami-Oshima Island, located in the far south off the main island of Japan.     

Long-term storage of sexual and asexual Trichogramma brassicae (Hymenoptera: Trichogrammatidae)

The effect of exposure duration to pre-storage (representing fall conditions) and storage (representing winter conditions) temperatures on the emergence rate in sexual and asexual Trichogramma brassicae Bezdenko (Hymenoptera: Trichogrammatidae) was studied under controlled laboratory conditions. Asexual T. brassicae was infected by Wolbachia, an endosymbiont bacterium. We considered 0, 30, 40, 50 and 60 days as exposure duration at 10°C and 0, 30, 60, 90 followed by 180 days as exposure duration at 4°C for both T. brassicae strains. Emergence rate was significantly affected by the presence of Wolbachia, the duration of exposure to 10°C, the duration of storage at 4°C and their interactions, but not by the interaction between strain × storage duration at 4°C. Emergence rate of adults was positively correlated with exposure duration at 10°C, but it gradually decreased as the cold storage duration (4°C) increased in both strains. In conclusion, we are able to store both asexual and sexual strains for longer periods of time at 4°C, but the emergence rate of sexual T. brassicae was greater than asexual in all the treatments. The presence of Wolbachia could have a negative effect on fitness of T. brassicae and reduces its emergence rate after long-term storage.     

Activity of four antimicrobial cocktails for tissue allograft decontamination against bacteria and Candida spp. of known susceptibility at different temperatures

Several antimicrobial cocktail solutions of differing composition and concentrations are widely used to decontaminate viable banked tissue allografts at different temperatures and times of exposure. We compared the efficiency of four cocktails comprising nine antimicrobials to kill suspensions of a panel of 27 strains of 13 bacterial species, and 3 Candida spp. at 4, 22 and 37 °C for 24 h. All but one bacterial strains were susceptible to one or more of the agents tested individually at concentrations at least fourfold below the recommended susceptibility breakpoint minimum inhibitory concentrations for drug/species combinations. Candida lusitaniae was resistant to nystatin and amphotericin. The concentrations of several of the cocktail constituents were often greatly in excess (50–1,000-fold) of that required to inhibit the growth of susceptible strains. All cocktails were ineffective against a pan-resistant strain of Enterococcus faecium and one of the four cocktails failed to kill two strains of methicillin resistant Staphylococcus aureus. Each cocktail was most efficient at 37 °C, less so at 22 °C, and poorly active at 4 °C. We conclude that the practice of decontamination of tissues with antimicrobials at low temperatures is not supported by in vitro susceptibility tests.     

Effect of temperature on germination,growth, and infectivity of the mosquito pathogen Tolypocladium cylindrosporum (deuteromycotina; hyphomycetes)

The mosquito pathogen Tolypocladium cylindrosporum was examined with regard to its response to temperature. Similar temperature ranges were found for growth, germination, and infectivity of blastospores and conidia. Germination occurred at 8° and 33°C but not at 6° and 35°C. Optimal germination and growth was noted between 24° and 27°C for both spore types. Infectivity of blastospores and conidia at different temperatures was examined by exposing L₂Aedes sierrensis larvae to concentrations of 5 × 10⁵ blastospores/ml or 5 × 10⁶ conidia/ml. Larvae were incubated at 12°, 15°, 25°, and 30°C. Infection occurred at all temperatures tested with LT₅₀ values ranging from 22.7 days (12°C) to 5.6 (25°C) days for conidia and 4.7 days (12°C) to 0.6 day (25°C) for blastospores. These results confirmed earlier findings that blastospores infected and killed host larvae more rapidly than conidia and suggested that this difference is largely due to the more rapid germination rate of blastospores. These experiments demonstrated that T. cylindrosporum can be active against mosquito larvae over a broad range of temperatures encompassing both the cold-water habitat of certain temperate mosquito species as well as the habitat of tropical vector species.     

Comparative in situ remediation potential of Pseudomonas putida 710A and Commamonas aquatica 710B using plant (Vigna radiata (L.) wilczek) assay

A greenhouse study was conducted to determine the effect of cadmium (Cd)-resistant Pseudomonas putida strain 710A and Commamonas aquatica strain 710B, used either alone or as a binary mixture on the toxicity of cadmium to mungbean [Vigna radiata (L.) wilczek] plants. The bacterial strains 710A and 710B, isolated from the Semra mines in Ranchi, India, were resistant to 0.5 mM and 1 mM, CdCl₂ respectively. Moreover, both strains grew well at 10 °C and 30 °C. Of the two bacterial strains, strain 710B showed 129.6 and 83.5 times higher P solubilizing activity than strain 710A, when grown in liquid broth supplemented with cadmium at 10 °C and 30 °C, respectively. Furthermore, 16S ribosomal DNA (rDNA) sequencing identified 710A as a Pseudomonas putida strain and 710B as a Commamonas aquatica strain. The strain 710A significantly (p?<?0.05) stimulated the growth of roots (35.2 %) and shoots (30 %) of mungbean plants grown in soil treated with 110 μM CdCl₂. However, the increase in the case of 710B was found to be 15.4 % and 5.17 %, respectively. The loss of chlorophyll content was replenished by up to 80 %, 66 %, and 77.3 % by inoculation of 710A, 710B and binary mixture, respectively. Moreover the strains were able to reduce Cd accumulation in roots and shoots. Most significantly, residual Cd concentration in soil was reduced in the presence of bioinoculants. However, in terms of efficiency, the strains were found to be in the following order: 710A?>?710A +710B?>?710B. The results suggest that P. putida 710A strain is a potentially effective candidate metal to be used for sequestering and as a growth-promoting bioinoculant in Cd polluted soil.