Mixed aerobic and anaerobic microbial communities in benzene-contaminated groundwater

Aims:  To investigate the factors affecting benzene biodegradation and microbial community composition in a contaminated aquifer.
Methods and Results:  We identified the microbial community in groundwater samples from a benzene-contaminated aquifer situated below a petrochemical plant. Eleven out of twelve groundwater samples with in situ dissolved oxygen concentrations between 0 and 2·57 mg l⁻¹ showed benzene degradation in aerobic microcosm experiments, whereas no degradation in anaerobic microcosms was observed. The lack of aerobic degradation in the remaining microcosm could be attributed to a pH of 12·1. Three groundwaters, examined by 16S rRNA gene clone libraries, with low in situ oxygen concentrations and high benzene levels, each had a different dominant aerobic (or denitrifying) population, either Pseudomonas , Polaromonas or Acidovorax species. These groundwaters also had syntrophic organisms, and aceticlastic methanogens were detected in two samples. The alkaline groundwater was dominated by organisms closely related to Hydrogenophaga .
Conclusions:  Results show that pH 12·1 is inimical to benzene biodegradation, and that oxygen concentrations below 0·03 mg l⁻¹ can support aerobic benzene-degrading communities.
Significance and Impact of the Study:  These findings will help to guide the treatment of contaminated groundwaters, and raise questions about the extent to which aerobes and anaerobes may interact to effect benzene degradation.     

Heterogeneous aerobic benzene-degrading communities in oxygen-depleted groundwaters

A sandstone aquifer beneath a petrochemicals plant (SIReN site, UK) is heterogeneously contaminated with benzene and oxygen-depleted. Despite low redox potentials in three of the most contaminated groundwaters (benzene concentrations from 17.8 to 294 mg L(-1)), we observed aerobic benzene degradation in microcosms, indicating the presence in situ of a latent community of obligate aerobic microorganisms or an active community of facultative aerobes responding rapidly to oxygen ingress. Moreover, benzene degradation occurred at the ambient pH of 8.9 and 9.4, considerably more alkaline conditions than previously reported. 16S rRNA analyses showed that the groundwater microcosm communities were distinct from each other, despite sharing the function of aerobic benzene degradation. From DNA fingerprinting, one consortium was dominated by Acidovorax spp., another by Pseudomonas spp.; these benzene-degrading consortia were similar to the in situ communities, perhaps indicating that these organisms are active in situ and degrading benzene microaerophilically or by denitrification. Conversely, in the third sample, benzene degradation occurred only after the community changed from a Rhodoferax-dominated community to a mix of Rhodococcus and Hydrogenophaga spp. Four of the main benzene-degrading strains were brought into culture: Hydrogenophaga and Pseudomonas spp., and two strains of Rhodococcus erythropolis, a ubiquitous and metabolically versatile organism.     

Degradation of BTEX compounds in liquid media and in peat biofilters

A mixed culture, enriched from Sphagnum peat moss, contaminated with gasoline vapours, degraded individual and mixed components of BTEX (benzene, toluene, ethylbenzene, xylene). Complete degradation of radiolabelled toluene by the mixed culture was observed in mineralisation studies. Individual isolates from a mixed culture containingPseudomonas maltophilia, P. testosteroni andP. putida biotype A exhibited contrasting BTEX degradation patterns. WhileP. putida biotype A degraded all of the BTEX compounds,P. maltophilia andP. testosteroni, appeared unable to degrade benzene and xylenes, respectively. When the peat, inoculated with the mixed culture, was used as a biofilter (6.2 cm diameter ×93 cm length) for degradation of toluene and ethylbenzene vapours, percentage removal efficiencies were 99 and 85, respectively. When the capacity of the biofilter to degrade a combination of BTEX compounds was evaluated, percentage removal efficiencies for toluene, ethylbenzene,p-xylene,o-xylene and benzene were 99, 85, 82, 80 and 78, respectively. The importance of using the mixed culture as an inoculum in the biofilter was established and also the relationship between contaminated vapour flow rate and percentage removal efficiency.     

Temperature effects and substrate interactions during the aerobic biotransformation of BTEX mixtures by toluene-enriched consortia and Rhodococcus rhodochrous

A microbial consortium derived from a gasoline-contaminated aquifer was enriched on toluene (T) in a chemostat at 20 degrees C and was found to degrade benzene (B), ethylbenzene (E), and xylenes (X). Studies conducted to determine the optimal temperature for microbial activity revealed that cell growth and toluene degradation were maximized at 35 degrees C. A consortium enriched at 35 degrees C exhibited increased degradation rates of benzene, toluene, ethylbenzene, and xylenes in single-substrate experiments; in BTEX mixtures, enhanced benzene, toluene, and xylene degradation rates were observed, but ethylbenzene degradation rates decreased. Substrate degradation patterns over a range of BTEX concentrations (0 to 80 mg/L) for individual aromatics were found to differ significantly from patterns for aromatics in mixtures. Individually, toluene was degraded fastest, followed by benzene, ethylbenzene, and the xylenes. In BTEX mixtures, degradation followed the order of ethylbenzene, toluene, and benzene, with the xylenes degraded last. A pure culture isolated from the 35 degrees C-enriched consortium was identified as Rhodococcus rhodochrous. This culture was shown to degrade each of the BTEX compounds, individually and in mixtures, following the same degradation patterns as the mixed cultures. Additionally, R. rhodochrous was shown to utilize benzene, toluene, and ethylbenzene as primary carbon and energy sources. Studies conducted with the 35 degrees C-enriched consortium and R. rhodochrous to evaluate potential substrate interactions caused by the concurrent presence of multiple BTEX compounds revealed a range of substrate interaction patterns including no interaction, stimulation, competitive inhibition, noncompetitive inhibition, and cometabolism. In the case of the consortium, benzene and toluene degradation rates were slightly enhanced by the presence of o-xylene, whereas the presence of toluene, benzene, or ethylbenzene had a negative effect on xylene degradation rates. Ethylbenzene was shown to be the most potent inhibitor of BTEX degradation by both the mixed and pure cultures. Attempted quantification of these inhibition effects in the case of the consortium suggested a mixture of competitive and noncompetitive inhibition kinetics. Benzene, toluene, and the xylenes had a negligible effect on the biodegradation of ethylbenzene by both cultures. Cometabolism of o-, m-, and p-xylene was shown to be a positive substrate interaction.     

Tandem biodegradation of BTEX components by two Pseudomonas sp

A co-culture of two Pseudomonas putida isolates was enriched from sediment on a mixture of benzene, toluene, ethylbenzene, m-xylene, p-xylene, and o-xylene. The co-culture readily degraded each of the compounds present. Benzene, toluene, and ethylbenzene were used as growth substrates by one isolate, while toluene, m-xylene, and p-xylene were used as growth substrates by the other. Neither isolate could grow on o-xylene, but it was removed in the presence of the other compounds presumably by co-metabolism. The findings presented here support other reports in which constructed communities were effectively used to degrade blends of between two and four of the components of BTEX. However, here the co-culture of two P. putida isolates effectively degraded a complete BTEX stream containing all six of the components. Received: 4 September 2001 / Accepted: 19 October 2001     

Kinetics of BTEX biodegradation by a coculture of <Emphasis Type="Italic">Pseudomonas putida</Emphasis> and<Emphasis Type="Italic"> Pseudomonas fluorescens</Emphasis> under hypoxic conditions

Pseudomonas putida and Pseudomonas fluorescens present as a coculture were studied for their abilities to degrade benzene, toluene, ethylbenzene, and xylenes (collectively known as BTEX) under various growth conditions. The coculture effectively degraded various concentrations of BTEX as sole carbon sources. However, all BTEX compounds showed substrate inhibition to the bacteria, in terms of specific growth, degradation rate, and cell net yield. Cell growth was completely inhibited at 500mgl^–1 of benzene, 600mgl^–1 of o-xylene, and 1000mgl^–1 of toluene. Without aeration, aerobic biodegradation of BTEX required additional oxygen provided as hydrogen peroxide in the medium. Under hypoxic conditions, however, nitrate could be used as an alternative electron acceptor for BTEX biodegradation when oxygen was limited and denitrification took place in the culture. The carbon mass balance study confirmed that benzene and toluene were completely mineralized to CO₂ and H₂O without producing any identifiable intermediate metabolites.     

Substrate interactions during the biodegradation of benzene,toluene, ethylbenzene,and xylene (BTEX) hydrocarbons by the fungus Cladophialophora sp. strain T1

The soil fungus Cladophialophora sp. strain T1 (= ATCC MYA-2335) was capable of growth on a model water-soluble fraction of gasoline that contained all six BTEX components (benzene, toluene, ethylbenzene, and the xylene isomers). Benzene was not metabolized, but the alkylated benzenes (toluene, ethylbenzene, and xylenes) were degraded by a combination of assimilation and cometabolism. Toluene and ethylbenzene were used as sources of carbon and energy, whereas the xylenes were cometabolized to different extents. o-Xylene and m-xylene were converted to phthalates as end metabolites; p-xylene was not degraded in complex BTEX mixtures but, in combination with toluene, appeared to be mineralized. The metabolic profiles and the inhibitory nature of the substrate interactions indicated that toluene, ethylbenzene, and xylene were degraded at the side chain by the same monooxygenase enzyme. Our findings suggest that soil fungi could contribute significantly to bioremediation of BTEX pollution.     

Substrate Interactions during the Biodegradation of Benzene, Toluene, Ethylbenzene, and Xylene (BTEX) Hydrocarbons by the Fungus Cladophialophora sp. Strain T1

The soil fungus Cladophialophora sp. strain T1 (= ATCC MYA-2335) was capable of growth on a model water-soluble fraction of gasoline that contained all six BTEX components (benzene, toluene, ethylbenzene, and the xylene isomers). Benzene was not metabolized, but the alkylated benzenes (toluene, ethylbenzene, and xylenes) were degraded by a combination of assimilation and cometabolism. Toluene and ethylbenzene were used as sources of carbon and energy, whereas the xylenes were cometabolized to different extents. o-Xylene and m-xylene were converted to phthalates as end metabolites; p-xylene was not degraded in complex BTEX mixtures but, in combination with toluene, appeared to be mineralized. The metabolic profiles and the inhibitory nature of the substrate interactions indicated that toluene, ethylbenzene, and xylene were degraded at the side chain by the same monooxygenase enzyme. Our findings suggest that soil fungi could contribute significantly to bioremediation of BTEX pollution.     

Biodegradation of BTEX at high salinity by an enrichment culture from hypersaline sediments of Rozel Point at Great Salt Lake

Aims: The primary goal of this research was to assess the biodegradation of benzene, toluene, ethylbenzene and xylenes in sediment from Great Salt Lake, near Rozel Point, UT. Methods and Results: An enrichment culture that degraded benzene or toluene as the sole carbon source at high salinity was developed from a sediment sample obtained from Rozel Point. The enrichment degraded benzene or toluene within 1, 2 and 5 weeks in the presence of 14%, 23% and 29% NaCl respectively. PCR studies using degenerate primers revealed that degradation occurred primarily via catechol and the meta‐cleavage pathway. Molecular analysis showed that the Gammaproteobacteria were the dominant members of the enrichment and that shifts in community composition occurred during benzene metabolism. Conclusions: This study demonstrated that micro‐organisms at Rozel Point have the ability to degrade hydrocarbons over a broad range of salinities (1–5 mol l^?1 NaCl) and that the members of the Gammaproteobacteria class play an important role in the degradation process. Significance and Impact of the Study: These results are significant as little is known about the fate of petroleum seeps at Rozel Point. Also, the identity of microbes and the key enzymes involved in the degradation steps are important for understanding natural attenuation potential of hydrocarbons.     

Isolation of bovine intestinal Lactobacillus plantarum and Pediococcus acidilactici with inhibitory activity against Escherichia coli O157 and F5

Aims:  The growth rate of bovine lactic acid bacteria (LAB) in five different culture conditions, and their inhibitory activity against Escherichia coli O157 and F5 in two assays was assessed to identify LAB for potential prophylactic use in cattle.
Methods and Results:  106 bovine-derived faecal/intestinal LAB were tested in vitro for tolerance to pH 2·0, pH 4·0, 0·15% and 0·3% bile, aerobic incubation, and for inhibitory activity against E. coli O157 ( n  = 3) and F5 ( n  = 1). While no LAB grew at pH 2·0, LAB survivability varied between 35% and 100% on the other tests. Exactly 7·6% (8/106) of LAB supernatants inhibited the growth of E. coli in two assays, whereas 6·6% (7/106) of isolates enhanced the growth of all E. coli strains. Partial 16s rRNA gene sequencing of six best isolates (95th percentile) revealed that five were Lactobacillus plantarum and one Pediococcus acidilactici.
Conclusion:  Lactobacillus plantarum with acid/bile and aerobic resistance and inhibitory activity against E. coli O157 and F5 inhabit the intestinal tract of healthy cattle. Some LAB may enhance E. coli growth.
Significance and Impact of the Study:  Lactobacillus plantarum and P. acidilactici are natural plant micro-organisms and studied silage inoculants. Their identification from gastrointestinal samples of healthy cattle is prophylactically promising.     

Anti-Helicobacter pylori activity of Lactobacillus delbrueckii subsp. bulgaricus strains: preliminary report

Aims:  To evaluate the activities of six Lactobacillus delbrueckii subsp. bulgaricus (LB) strains against 30 Helicobacter pylori strains by agar-well diffusion method.
Methods and Results:  LB cultures [4 × 10⁸–4 × 10⁹ CFU ml⁻¹) either were prepared in milk at their native pH, 3·8–5·0, or were adjusted to pH 6·4–7·7. At low and neutralized pH, LB strains inhibited the growth by 40–86·7% and 16·7–66·7% of H. pylori strains, respectively. LB activity was strain-dependent. At low and neutralized pH, one and five H. pylori strains, respectively, were not inhibited by any LB strain. LB2 and LB3, taken together, were active against most metronidazole and clarithromycin resistant strains.
Conclusions:  All LB strains inhibited a number of H. pylori strains, including also antibiotic resistant strains. LB activity was strain-dependent and better at low pH. At low pH values, the most active LB strains were LB1, LB2 and LB3, inhibiting 86·7% of H. pylori strains, while at neutralized pH values, the most active LB strains were LB2 and LB3, inhibiting 53·3 and 66·7% of H. pylori strains, respectively.
Significance and Impact of the Study:  LB could be utilized in the treatment or prophylaxis of H. pylori infection and warrants clinical investigations.     

Isolation and characterization of four novel Gram-positive bacteria associated with the rhizosphere of two endemorelict plants capable of degrading a broad range of aromatic substrates

Four new Gram-positive, phenol-degrading strains were isolated from the rhizospheres of endemorelict plants Ramonda serbica and Ramonda nathaliae known to exude high amounts of phenolics in the soil. Isolates were designated Bacillus sp. PS1, Bacillus sp. PS11, Streptomyces sp. PS12, and Streptomyces sp. PN1 based on 16S rDNA sequence and biochemical analysis. In addition to their ability to tolerate and utilize high amounts of phenol of either up to 800 or up to 1,400 mg l⁻¹ without apparent inhibition in growth, all four strains were also able to degrade a broad range of aromatic substrates including benzene, toluene, ethylbenzene, xylenes, styrene, halogenated benzenes, and naphthalene. Isolates were able to grow in pure culture and in defined mixed culture on phenol and on the mixture of BTEX (benzene, toluene, ethylbenzene, and xylenes) compounds as a sole source of carbon and energy. Pure culture of Bacillus sp. PS11 yielded 1.5-fold higher biomass amounts in comparison to mixed culture, under all conditions. Strains successfully degraded phenol in the soil model system (2 g kg⁻¹) within 6 days. Activities of phenol hydroxylase, catechol 1,2-dioxygenase, and catechol 2,3-dioxygenase were detected and analyzed from the crude cell extract of the isolates. While all four strains use ortho degradation pathway, enzyme indicative of meta degradation pathway (catechol 2,3-dioxygenase) was also detected in Bacillus sp. PS11 and Streptomyces sp. PN1. Phenol degradation activities were induced 2 h after supplementation by phenol, but not by catechol. Catechol slightly inhibited activity of catechol 2,3-dioxygenase in strains PS11 and PN1.     

Biotreatment of groundwater contaminated with MTBE: interaction of common environmental co-contaminants

Contamination of groundwater with the gasoline additive methyl tert-butyl ether (MTBE) is often accompanied by many aromatic components such as benzene, toluene, ethylbenzene, o-xylene, m-xylene and p-xylene (BTEX). In this study, a laboratory-scale biotrickling filter for groundwater treatment inoculated with a microbial consortium degrading MTBE was studied. Individual or mixtures of BTEX compounds were transiently loaded in combination with MTBE. The results indicated that single BTEX compound or BTEX mixtures inhibited MTBE degradation to varying degrees, but none of them completely repressed the metabolic degradation in the biotrickling filter. Tert-butyl alcohol (TBA), a frequent co-contaminant of MTBE had no inhibitory effect on MTBE degradation. The bacterial consortium was stable and showed promising capabilities to remove TBA, ethylbenzene and toluene, and partially degraded benzene and xylenes without significant lag time. The study suggests that it is feasible to deploy a mixed bacterial consortia to degrade MTBE, BTEX and TBA at the same time.     

Characterization of some culture factors affecting oxalate degradation by the mycoparasite Coniothyrium minitans

Aims:  To find possible approaches to utilize the mechanism of oxalate degradation by Coniothyrium minitans (Cm) in controlling the plant pathogen Sclerotinia sclerotiorum (Ss).
Methods and Results:  Differences in oxalate degradation by different Cm strains and effects of the initial oxalate concentration, ambient pH and nutrient factors on mycelial growth and oxalate degradation by Cm were studied in shaken cultures. Results showed that two wild-type Cm strains, Chy-1 and ZS-1, did not differ in oxalate degradation in modified potato dextrose broth (mPDB) amended with oxalic acid (OA). Cm could grow in mPDB amended with sodium oxalate (SO-mPDB) at pH 6·5 or with ammonium oxalate (AO-PDB) at pH 6·2, but oxalate degradation was very low; oxalate degradation was greatly enhanced in SO- or AO-mPDB with pH being lowered to 2·8–2·9. Similarly, oxalate degradation was higher than 90% in OA-amended mPDB at pH 4·4 but was reduced to be <22% at pH 7·0. Five carbon sources and three nitrogen sources investigated and nutrients from mycelia and sclerotia of Ss were favorable for the growth of Cm and OA degradation by Cm.
Conclusions:  Cm can degrade oxalate under acidic pH. Exudates from mycelia or sclerotia of Ss may serve as nutrients for Cm mycelial growth and degradation of oxalate secreted by Ss.
Significance and Impact of the Study:  The finding of oxalate degradation laid a foundation for mining-related genes in Cm for engineering plant resistance against Ss. Elucidation of the importance of acidic pH and nutrients from Ss in oxalate degradation by Cm will help to understand the interaction between Cm and Ss.     

Diversity of hydrocarbon-degrading Klebsiella strains isolated from hydrocarbon-contaminated estuaries

Aims:  To investigate the diversity and the catabolic capacity of oil-degrading Klebsiella strains isolated from hydrocarbon-contaminated sediments in Santos–São Vicente estuary systems in Brazil.
Methods and Results:  Klebsiella strains obtained from the estuary were characterized using 16S rRNA gene sequencing and BOX-PCR patterns, testing their catabolic capacity to degrade toluene, xylene, naphthalene and nonane, and identifying the catabolic genes present in the oil-degrading strains. Results show that Klebsiella strains were widespread in the estuary. Twenty-one isolates from the Klebsiella genus were obtained; 14 had unique BOX patterns and were further investigated. Among four distinct catabolic genes tested ( todC 1, ndoB , xylE and alkB 1), only the todC 1 gene could be amplified in two Klebsiella strains. The biodegradation assay showed that most of the strains had the ability to degrade all of the tested hydrocarbons; however, the strains displayed different efficiencies.
Conclusions:  The oil-degrading Klebsiella isolates obtained from the estuary were closely related to Klebsiella pneumoniae and Klebsiella ornithinolytica . The isolates demonstrated a substantial degree of catabolic plasticity for hydrocarbon degradation.
Significance and Impact of the Study:  The results of this study show that several strains from the Klebsiella genus are able to degrade diverse hydrocarbon compounds. These findings indicate that Klebsiella spp. can be an important part of the oil-degrading microbial community in estuarine areas exposed to sewage.     

Biodegradation of benzene by halophilic and halotolerant bacteria under aerobic conditions

A highly enriched halophilic culture was established with benzene as the sole carbon source by using a brine soil obtained from an oil production facility in Oklahoma. The enrichment completely degraded benzene, toluene, ethylbenzene, and xylenes within 1 to 2 weeks. Also, [14C]benzene was converted to 14CO2, suggesting the culture's ability to mineralize benzene. Community structure analysis revealed that Marinobacter spp. were the dominant members of the enrichment.     

Comparison of methods to detect resistance of Penicillium expansum to thiabendazole

Aims:  Because of the lack of a standard method, the aim of this work is to evaluate the suitability of the broth microdilution method CLSI M38-A in determining the resistance level of some Penicillium expansum isolates to thiabendazole (TBZ). The ability of the isolates to produce patulin (PAT) and citrinin (CIT) has been also assessed.
Methods and Results:  Penicillium expansum isolates (128) were assayed (apples, pears, grapes and five reference strains). It was observed that 69·4% of the strains isolated from apples and pears were resistant to TBZ. Sensitive isolates were inhibited at 0·25–0·5 μg ml⁻¹ whilst resistant isolates still grew at 512 μg ml⁻¹. PAT was produced by all P. expansum isolates. CIT was detected in 98·8% of TBZ-resistant isolates and in 89·1% of the TBZ-sensitive isolates.
Conclusions:  The preliminary screening method combined with the adaptation of the method CLSI M38-A, can be a good strategy to be used in assessing the in vitro activity of TBZ against a large number of isolates.
Significance and Impact of the Study:  The proposed methodology can be a contribution to the standardization of susceptibility tests to fungicides against P. expansum.     

Phenotypic variations of enterococci in surface waters: analysis of biochemical fingerprinting data from multi-catchments

Aims:  The aim of this study was to identify the prevalence of environmentally adapted enterococci strains by analysing biochemical fingerprinting (BF) data of 3952 enterococci isolates collected over 5 years from the six catchments in Southeast Queensland, Australia.
Methods and Results:  A BF method was used to type 3952 enterococci isolates from six catchments. The environmental isolates were compared with a large existing BF library comprised of 5803 enterococci isolates from 10 host groups. Environmental isolates belonged to 801 biochemical phenotypes (BPTs), of which, an average of 29.2% was specific to each catchment. When compared with the BF library, an average of 79·5% BPTs from each catchment was identical to those in the library (i.e. host-origin BPTs). The remaining 20·5% was regarded as non-host origin BPTs, as they were not in the library and constituted only 5·3% of the total isolates tested for each catchment.
Conclusions:  Our data suggest that less than 5% of studied environmental strains was not identical to those in the library and seemed to be of environmental origin. From a microbial source tracking context, such low level of environmentally adapted strains can have a minimal impact on the performance of the library-based methods if a large number of isolates were tested from both the host groups and environmental waters.
Significance and Impact of the Study:  These data shed light on the importance of the size and representativeness of library–based source-tracking methods and their implications for the identification of faecal pollution in environmental waters.     

Effect of environmental stresses on the sensitivity of Enterobacter sakazakii in powdered infant milk formula to gamma radiation

Aim:  To evaluate the effect of starvation, heat, cold, acid, alkaline, chlorine and ethanol stresses on the resistance of Enterobacter sakazakii in powdered infant milk formula (PIMF) towards gamma radiation.
Methods and Results:  Stressed cells of E. sakazakii ATCC 51329 and four other food isolate strains were mixed individually with PIMF, kept overnight at room temperature, and then exposed to gamma radiation up to 7·5 kGy. The D ₁₀-values were determined using linear regression and for the stressed E. sakazakii strains these values ranged from 0·82 to 1·95 kGy.
Conclusions:  Environmental stresses did not significantly change the sensitivity of most E. sakazakii strains to ionizing radiation.
Significance and Impact of the Study:  Data obtained established that most forms of environmental stress are unlikely to significantly enhance the resistance of E. sakazakii strains to lethal, low dose irradiation treatment.     

Comparison of Lactococcus garvieae strains isolated in northern Italy from dairy products and fishes through molecular typing

Aims:  To investigate the genetic relatedness between Lactococcus garvieae strains isolated from fish and dairy samples collected in northern Italy, using random-amplified polymorphic DNA (RAPD)-polymerase chain reaction (PCR), Sau -PCR and amplified fragment length polymorphism (AFLP).
Methods and Results:  Eighty-one isolates from bovine and caprine dairy products ( n  = 53) and from diseased rainbow trouts and other fishes ( n  = 28) were examined. All methods showed a typeability of 100%, repeatability ranging from 84·4% to 97·5% and discriminatory powers from 0·798 to 0·986. Dairy and fish strains revealed a low genetic relatedness as they are often grouped into distinct clusters. RAPD analysis discriminated 52 genotypes when primer M13 was used, whereas with primer P5 only 27 genotypes were identified. When Sau -PCR was performed, 13 genotypes were detected while AFLP analysis allowed the differentiation of 32 genotypes.
Conclusion:  L. garvieae strains isolated from dairy samples are generally not related to those collected from fish lactococcosis outbreaks.
Significance and Impact of the Study:  L. garvieae strains exhibit a genetic diversity related to the specific animal host they colonize. RAPD M13 fingerprinting proved to be a molecular tool for comparing isolates, whereas Sau -PCR and AFLP analyses were useful techniques to investigate the distribution of L. garvieae populations in the environment.