María Julia Amoroso

Isolation of four aquatic streptomycetes strains capable of growth on organochlorine pesticides.

Ninety-three wild-type isolates identified as actinomycetes were tested against 11 organochlorine pesticides (OPs): aldrin, chlordane, DDD, DDE, DDT, dieldrin, heptachlor, and heptachlor epoxides, lindane, and methoxychlor. Qualitative screening agar assays displayed 62-78% tolerance of strains to OPs. Four strains designed M4, M7, M9 and M15 were selected based on multi-OP-tolerance, and identified as members of the streptomycetes group. Different growth profiles were observed in cultures of the four selected streptomycetes cultured in synthetic medium containing 5-50 microg x l(-1) aldrin or chlordane or lindane. Increase of aldrin removal by the selected microorganisms was concomitant with the 4.8-36.0 microg x l(-1) pesticide concentration range. After 72 h of streptomycete M7 growth in synthetic medium containing 48.0 microg x l(-1) aldrin, the remaining OP concentration in the supernatant was approximately 10% of the initial concentration. Also, in stationary growth phase less than 2.5 microg x l(-1) aldrin residual concentration was detected in the medium.

Bioremediation of chromium(VI) contaminated soil by Streptomyces sp. MC1

This work provides quantitative information on Cr(VI) reduction in soil samples by an indigenous actinomycete. Streptomyces sp. MC1, previously isolated from sugarcane, has shown ability to reduce Cr(VI) in liquid minimal medium. A reduction of 100 and 75% was obtained at initial Cr(VI) concentrations of 5 and 50 mg l–1, respectively, after 48 h of incubation. Bioremediation ability of Streptomyces sp. MC1 was assayed in soil extracts and soil samples. Relative growth of Streptomyces sp. MC1 was 77 and 38% when grown in soil extract with 10 and 50 mg l–1 of Cr(VI), respectively. MC1 was able to reduce 30% of Cr(VI) after 96 h of incubation with 10 mg l–1 of Cr(VI), and reduction coincided with the exponential growth phase at pH 7 and 30 °C.

Chromium accumulation by two Streptomyces spp. isolated from riverine sediments

Strains designated R22 and R25, isolated from Salí River sediments, Argentina, were highly resistant to chromium. These strains were shown by 16S rRNA sequencing studies to be Streptomyces spp.; this affiliation was consistent with morphological and chemical characteristics. Growth of strains R22 and R25 in medium containing 100 mg l−1 chromate was reduced by only 23% and 34%, respectively, compared with growth in medium without added chromium. Streptomyces sp. strains R22 and R25 both accumulated chromium with yields of 10.0 and 5.6 mg Cr g−1 of dry weight, respectively, and a chromate concentration of 50 mg ml−1. Cell fractionation studies with strain R22 showed that the great majority of the chromium were associated with the cell wall fraction. Streptomyces strains R22 and R25 may have applications in bioremediation of chromium contamination. Journal of Industrial Microbiology & Biotechnology (2001) 26, 210–215.

Actinobacteria: Current research and perspectives for bioremediation of pesticides and heavy metals

Actinobacteria exhibit cosmopolitan distribution since their members are widely distributed in aquatic and terrestrial ecosystems. In the environment they play relevant ecological roles including recycling of substances, degradation of complex polymers, and production of bioactive molecules. Biotechnological potential of actinobacteria in the environment was demonstrated by their ability to remove organic and inorganic pollutants. This ability is the reason why actinobacteria have received special attention as candidates for bioremediation, which has gained importance because of the widespread release of contaminants into the environment. Among organic contaminants, pesticides are widely used for pest control, although the negative impact of these chemicals in the environmental balance is increasingly becoming apparent. Similarly, the extensive application of heavy metals in industrial processes lead to highly contaminated areas worldwide. Several studies focused in the use of actinobacteria for cleaning up the environment were performed in the last 15 years. Strategies such as bioaugmentation, biostimulation, cell immobilization, production of biosurfactants, design of defined mixed cultures and the use of plant-microbe systems were developed to enhance the capabilities of actinobacteria in bioremediation. In this review, we compiled and discussed works focused in the study of different bioremediation strategies using actinobacteria and how they contributed to the improvement of the already existing strategies. In addition, we discuss the importance of omic studies to elucidate mechanisms and regulations that bacteria use to cope with pollutant toxicity, since they are still little known in actinobacteria. A brief account of sources and harmful effects of pesticides and heavy metals is also given.

Amycolatopsis tucumanensis sp. nov., a copper-resistant actinobacterium isolated from polluted sediments.

A novel actinomycete strain, ABO(T), isolated from copper-polluted sediments showed remarkable copper resistance as well as high bioaccumulation abilities. Classical taxonomic methods, including chemotaxonomy and molecular techniques, were used to characterize the isolate. Strain ABO(T) developed a honey-yellow substrate mycelium on all ISP media tested. Abundant, white, aerial mycelium was only formed on ISP 2, 5 and 7 and MM agar. Both types of hyphae fragmented into squarish rod-shaped elements. The aerial mycelium displayed spore-like structures with smooth surfaces in long, straight to flexuous chains. The organism has a type-IV cell wall lacking mycolic acids and type-A whole-cell sugar pattern (meso-diaminopimelic acid, arabinose and galactose) in addition to a phospholipid type-II profile. 16S rRNA gene sequence studies indicated that this organism is a member of the family Pseudonocardiaceae and that it forms a monophyletic clade with Amycolatopsis eurytherma NT202(T). The DNA-DNA relatedness of strain ABO(T) to A. eurytherma DSM 44348(T) was 39.5 %. It is evident from these genotypic and phenotypic data that strain ABO(T) represents a novel species in the genus Amycolatopsis, for which the name proposed is Amycolatopsis tucumanensis sp. nov. The type strain is ABO(T) (=DSM 45259(T) =LMG 24814(T)).

Bioaugmentation of copper polluted soil microcosms with Amycolatopsis tucumanensis to diminish phytoavailable copper for Zea mays plants

Amycolatopsis tucumanensis DSM 45259, the strain of a recently recognized novel species of the genus Amycolatopsis with remarkable copper resistance, was used to bioaugment soil microcosms experimentally polluted with copper and for studying the ability of this strain to effectively diminish phytoavailable copper from soils. Our results demonstrated that A. tucumanensis was capable of profusely colonizing both, copper polluted and non-polluted soil. Copper bioimmobilization ability of A. tucumanensis on soil was assessed measuring the bioavailable copper in the soil solution extracted from polluted soil by using chemical and physical methods and, in this way, 31% lower amounts of the metal were found in soil solution as compared to non-bioaugmented soil. The results obtained when using Zea mays as bioindicator correlated well with the values obtained by the chemical and physical procedures: 20% and 17% lower tissue contents of copper were measured in roots and leaves, respectively. These data confirmed the efficiency of the bioremediation process using A. tucumanensis and at the same time proved that chemical, physical and biological methods for assessing copper bioavailability in soils were correlated. These results suggest a potential use of this strain at large scale in copper soil bioremediation strategies. To our knowledge, this work is the first to apply and to probe the colonization ability of an Amycolatopsis strain in soil microcosms and constitutes the first application of an Amycolatopsis strain on bioremediation of polluted soils.

Lindane removal by pure and mixed cultures of immobilized actinobacteria

Lindane (γ-HCH) is an organochlorine insecticide that has been widely used in developing countries. It is known to persist in the environment and can cause serious health problems. One of the strategies adopted to remove lindane from the environment is bioremediation using microorganisms. Immobilized cells present advantages over free suspended cells, like their high degradation efficiency and protection against toxins. The aims of this work were: (1) To evaluate the ability of Streptomyces strains immobilized in four different matrices to remove lindane, (2) To select the support with optimum lindane removal by pure cultures, (3) To assay the selected support with consortia and (4) To evaluate the reusability of the immobilized cells. Four Streptomyces sp. strains had previously shown their ability to grow in the presence of lindane. Lindane removal by microorganisms immobilized was significantly higher than in free cells. Specifically immobilized cells in cloth sachets showed an improvement of around 25% in lindane removal compared to the abiotic control. Three strains showed significantly higher microbial growth when they were entrapped in silicone tubes. Strains immobilized in PVA-alginate demonstrated lowest growth. Mixed cultures immobilized inside cloth sachets showed no significant enhancement compared to pure cultures, reaching a maximum removal of 81% after 96 h for consortium I, consisting of the four immobilized strains together. Nevertheless, the cells could be reused for two additional cycles of 96 h each, obtaining a maximum removal efficiency of 71.5% when each of the four strains was immobilized in a separate bag (consortium III).

Responses of Candida fukuyamaensis RCL-3 and Rhodotorula mucilaginosa RCL-11 to copper stress.

The effect of high Cu(II) concentrations on superoxide dismutase (SOD) and catalase (CAT) activity in Candida fukuyamaensis RCL‐3 and Rhodotorula mucilaginosa RCL‐11, previously isolated from a copper filter at a mine plant in Argentina, was studied. Addition of 0.1, 0.2 and 0.5 mM Cu(II) to the culture medium increased total SOD and CAT activity in both strains. Native polyacrylamide gel electrophoresis revealed two bands with SOD activity for C. fukuyamaensis RCL‐3 and only one for R. mucilaginosa RCL‐11; the three bands corresponded to MnSOD.

Production and partial characterization of bioemulsifier from a chromium-resistant actinobacteria

Surface-active compounds such as synthetic emulsifiers have been used for several decades, both for the degradation of hydrocarbons and increasing desorption of soil-bound metals. However, due to their high toxicity, low degradability, and production costs unaffordable for use in larger ecosystems, synthetic emulsifiers have been gradually replaced by those derived from natural sources such as plants or microbes. In previous studies, the bacterium Streptomyces sp. MC1 has shown the ability to reduce and/or accumulate Cr(VI), a highly promising advance in the development of methods for environmental clean-up of sites contaminated with chromium. Here, new studies on the production of emulsifier from this strain are presented. The cultivation factors that have a significant influence on emulsifier biosynthesis, as well as the interactions among them, were studied by factorial design. Based upon optimization studies, maximum bioemulsifier production was detected in the culture medium having an initial pH of 8 with phosphate 2.0 g L(-1) and Ca(+2) 1.0 g L(-1) added, with an emulsification index about 3.5 times greater compared to the basal value. Interestingly, in the presence of 5.0 g L(-1) Cr(VI), Streptomyces sp. MC1 retained about 65% of its emulsifier production ability. Partially purified emulsifier presented high thermo-stability and partial water solubility. These findings could have promising future prospects for the remediation of organic- and metal-contaminated sites.

Potential application of a bioemulsifier-producing actinobacterium for treatment of vinasse

Vinasse is a complex effluent created during production of ethyl alcohol, which can present serious pollution hazard in areas where it is discharged. A variety of technologies, many based upon recovery of the effluent via microbial pathways, are continually being evaluated in order to mitigate the pollution potential of vinasse. The present work reports on initial advances related to the effectiveness of the actinobacterium Streptomyces sp. MC1 for vinasse treatment. Alternative use of raw vinasse as a substrate for producing metabolites of biotechnological interest such as bioemulsifiers, was also evaluated. The strain was able to grow at very high vinasse concentrations (until 50% v/v) and remove over 50% of the biodegradable organic matter in a time period as short as 4 d. Potentially toxic metals such as Mn, Fe, Zn, As, and Pb were also effectively removed during bacterial growth. Decrease in the pollution potential of treated vinasse compared to raw effluent, was reflected in a significant increase in the vigour index of Lactuca sativa (letucce) used as bioremediation indicator. Finally, significant bioemulsifier production was detected when this strain was incubated in a vinasse-based culture medium. These results represent the first advances on the recovery and re-valuation of an actual effluent, by using an actinobacterium from our collection of cultures.