An　additive-　and　pollution-free　method　for　the　preparation　of　biogenic　silver　and　silver　chloride　nanoparticles　(Ag@AgCl　NPs)　was　developed　from　the　bacteria　Shewanella　sp.　Arc9-LZ,　which　was　isolated　from　the　deep　sea　of　the　Arctic　Ocean.　The　optimal　synthesizing　conditions　were　explored,　including　light,　pH,　Ag+　concentration　and　time.　The　nanoparticles　were　studied　by　means　of　ultraviolet-visible　(UV-Vis)　spectrophotometry,　energy　dispersive　spectrometry　(EDS),　X-ray　diffraction　(XRD)　and　inductively　coupled　plasma　optical　emission　spectrometers　(ICP-OES).　The　transmission　electron　microscope　(TEM)　showed　that　the　nanoparticles　were　spherical　and　well　dispersed,　with　particle　sizes　less　than　20.00　nm.　With　Ag@AgCl　nanoparticles,　the　kinetic　rate　constants　for　congo　red　(CR)　and　rhodamine　B　(RhB)　dye　degradation　were　2.74　x　10(-1)　min(-1)　and　7.78　x　10(-1)　min(-1),　respectively.　The　maximum　decolourization　efficiencies　of　CR　and　RhB　were　93.36%　and　99.52%,　respectively.　Ag@AgCl　nanoparticles　also　showed　high　antibacterial　activities　against　the　Gram-positive　and　Gram-negative　bacteria.　The　Fourier　transform　infrared　spectroscopy　(FTIR)　spectrum　indicated　that　the　O-H,　N-H　and　-COO-　groups　in　the　supernatant　of　Arc9-LZ　might　participate　in　the　reduction,　stabilization　and　capping　of　nanoparticles.　We　mapped　the　schematic　diagram　on　possible　mechanisms　for　synthesizing　Ag@AgCl　NPs.