Summary auto-generated
Researchers isolated polyaromatic hydrocarbon (PAH)-degrading bacteria from petroleum-contaminated estuarine sediment and salt marsh plant rhizospheres using naphthalene, phenanthrene, or biphenyl as enrichment substrates. Two morphologically distinct groups of spore-forming Paenibacillus bacteria emerged: mucoid isolates that degraded naphthalene and non-mucoid isolates that degraded phenanthrene. Using fatty acid methyl ester analysis, 16S rRNA gene sequencing, phenotypic characterization, and DNA-DNA hybridization, the researchers determined that mucoid isolates formed a distinct cluster separate from known Paenibacillus species and from P. validus (identified among the non-mucoid isolates). The mucoid group showed only 6% DNA similarity to P. validus type strain, 94% 16S rRNA similarity, and distinct fatty acid profiles and phenotypic traits. Based on comprehensive morphological, phenotypic, and molecular evidence, the naphthalene-degrading mucoid isolates represent a novel species, designated Paenibacillus naphthalenovorans sp. nov., with type strain PR-N1ᵀ.
Key findings
- Two distinct Paenibacillus groups were isolated: mucoid naphthalene-degraders and non-mucoid phenanthrene-degraders identified as P. validus
- Mucoid isolates form a phylogenetically distinct cluster with only 6% DNA-DNA hybridization similarity to P. validus type strain
- The novel mucoid group exhibits unique fatty acid profiles (elevated 15:0 anteiso, 16:1ω11c, and 16:0) and distinct phenotypic characteristics differentiating them from related species
- 16S rRNA gene sequence analysis revealed 94% similarity to P. validus but phylogenetic clustering shows the mucoid group as a separate lineage within Paenibacillus
- Paenibacillus naphthalenovorans sp. nov. is proposed as a new species, with strain PR-N1ᵀ designated as the type strain
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Abstract
Bacteria belonging to the genus Paenibacillus were isolated by enrichment from petroleum-hydrocarbon-contaminated sediment and salt marsh rhizosphere using either naphthalene or phenanthrene as the sole carbon source, and were characterized using phenotypic, morphological and molecular techniques. The isolates were grouped by their colony morphologies and polyaromatic hydrocarbon-degradation patterns. Phenanthrene-degrading isolates produced mottled colonies on solid media and were identified as P. validus by fatty acid methyl ester and 16S rRNA gene sequence analyses. In contrast, the naphthalene-degrading isolates with mucoid colony morphology were distantly related to Paenibacillus validus, according to fatty acid methyl ester and 16S rRNA gene sequence analyses. The predominant fatty acids of the mucoid isolates were 15:0 anteiso, 16:1omega11c, 16:0 and 17:0 anteiso, constituting, on average, 50.5, 12.0, 11.2 and 6.5% of the total, respectively. The G+C contents of their DNA ranged from 47 to 52 mol%. The 16S rDNA sequence analysis revealed the highest (< 94%) similarity to P. validus. In addition, phylogenetic analyses based on 16S rDNA sequences showed that the mucoid isolates formed a distinct cluster within Paenibacillus. DNA--DNA hybridization experiments showed only a 6% DNA similarity between the type strain of P. validus and mucoid strain PR-N1. On the basis of the morphological, phenotypic and molecular data, the naphthalene-degrading isolates merit classification as a new Paenibacillus species, for which the name Paenibacillus naphthalenovorans sp. nov. is proposed, with PR-N1(T) (=ATCC BAA-206(T)=DSM 14203(T)) as the type strain.