Isolation, cytotoxic activity and phylogenetic analysis of <i>Bacillus sp.</i>bacteria associated with the red sea sponge <i>Amphimedon ochracea</i>

Most of marine sponges harbor dense and diverse microbial communities of bioactivity importance. Four Gram positive bacterial cultures (HA-21, HA-68, HA- MS-105 and HA-MS-119) were isolated from the sponge Amphimedon ochracea, collected from the Red Sea coast of Egypt. Bacterial species were identified based on the phylogenetic analysis of the nucleotide sequences of their 16S rDNA genes. The Sequences similarity values of 98% - 100% to other strains in the NCBI database showed strong similarities with the 16S rDNA genes of firmicutes (Bacillus sp.). The four bacterial species were submitted to the GenBank database and had accession numbers of: HA-21 [JQ-768238];HA-68 [JQ751264];HA-MS-105 [JQ768239];HAMS-119 [JQ768240]. The cytotoxic activities of the bacterial isolates were tested against three established human cancer cell lines;HepG2 (hepatocellular carcinoma), HCT (colon carcinoma) and MCF-7 (breast carcinoma). The inhibitory effect on these cell lines, measured by MTT cell assay protocol, revealed promising cytotoxic activity of the four isolates (IC50 values (μg/mL) were: HA-21: 13.2, 9.3 and 12.2;HA-68: 10.42, 4.3 and 5.5;HA-MS-105: 46.9, 28.6 and 21.3;HAMS-119: 10.42, 6.3 and 22.1;respectively). The recovery of bacterial strains with cytotoxic activity suggests that marine invertebrates remain a rich source for the isolation of culturable isolates capable of producing novel bioactive secondary metabolites.

Phylogenomic analyses shed light on the relationships of chiton superfamilies and shell‑eye evolution

Mollusca is the second-largest animal phylum with over 100,000 extant species representing eight classes.Across 1000 extant species in the class Polyplacophora,chitons have a relatively constrained morphology but with some notable deviations.Several genera possess“shell eyes”,i.e.,true eyes with a lens and retina that are embedded within the dorsal shells.The phylogeny of the major chiton clades is mostly well established,in a set of superfamily-level and higher level taxa supported by various approaches,including morphological studies,multiple gene markers,mitogenome-phylogeny,and phylotranscriptomic approaches.However,one critical lineage has remained unclear,namely Schizochiton which was controversially suggested as being the potential independent origin of chiton shell eyes.Here,with the draft genome sequencing of Schizochiton incisus(superfamily Schizochitonoidea)plus assemblies of transcriptome data from other polyplacophorans,we present phylogenetic reconstructions using both mitochondrial genomes and phylogenomic approaches with multiple methods.We found that phylogenetic trees from mitogenomic data are inconsistent,reflecting larger scale confounding factors in molluscan mitogenomes.However,a consistent and robust topology was generated with protein-coding genes using different models and methods.Our results support Schizochitonoidea as the sister group to other Chitonoidea in Chitonina,in agreement with the established classification.Combined with evidence from fossils,our phylogenetic results suggest that the earliest origin of shell eyes is in Schizochitonoidea,and that these structures were also gained secondarily in other genera in Chitonoidea.Our results have generated a holistic review of the internal relationship within Polyplacophora,and a better understanding of the evolution of Polyplacophora.