title: Metabolic differences between attached and free-living marine bacteria: inadequacy of liquid cultures for describing in situ bacterial activity.
abstract: Marinobacter sp. strain CAB was cultivated with or without porous glass beads as solid support. Two substrates were used: the hydrophilic sodium lactate and a hydrophobic C(18)-isoprenoid ketone (6,10,14-trimethylpentadecan-2-one (TMP)). The substrate adsorption onto the beads was measured. Bacterial adhesion was determined by a direct count technique and amounted to 70% of total cells. In the immobilised cell cultures (ICC), generation times were 1.5 and 1.8 times shorter than in the planktonic cultures (FCC) with sodium lactate and with TMP, respectively. In ICC, the growth yields were lower (15.3(FCC) x 10(9) and 0.8(ICC) x 10(9) bacteria mg(-1) of sodium lactate; 50(FCC) x 10(9) and 35(ICC) x 10(9) bacteria mg(-1) of TMP). The mineralisation of substrates was estimated after mass spectrometric determination of the CO2 production rates of both free and immobilised cell cultures. The results indicated a higher specific CO2 production rate in the ICC with sodium lactate (3.1(FCC)+/-0.2 and 3.5(ICC)+/-0.3 nmol CO2 mg(-1) protein min(-1)) but not in the ICC with TMP (1.9(FCC)+/-0.7 and 0.5(ICC)+/-0.3 nmol CO2 mg(-1) protein min(-1)). The affinities for the two substrates were lower in the presence of the solid support (K(m,ICC)=18.2+/-0.2 microM and 37.1+/-2.0 microM, for sodium lactate and TMP, respectively) than without support (K(m,FCC)=8.5+/-1.5 microM and 8.4+/-1.2 microM, for sodium lactate and TMP, respectively). Moreover, the presence of a solid support showed a lower inhibition by the TMP (K(i,FCC)=3.8+/-1.0 microM and K(i,ICC)=12.2+/-2.5 microM) which may explain why the immobilised cell cultures degraded hydrophobic TMP more efficiently than the planktonic cultures.
authors.affiliation: Laboratoire d'Océanologie et de Biogeochimie, CNRS-UMR 6535, Centre d'Océanologie de Marseille, Campus de Luminy, Case 901, 13288 cedex 9, Marseille, France. pbonin@com.univ-mrs.fr
authors.forename: P
authors.initials: P
authors.lastname: Bonin
authors.forename: J F
authors.initials: JF
authors.lastname: Rontani
authors.forename: L
authors.initials: L
authors.lastname: Bordenave
mesh_terms: D001422:Bacterial Adhesion / Q000502:physiology; D001431:Bacteriological Techniques; D002245:Carbon Dioxide / Q000378:metabolism; D018914:Cells, Immobilized / Q000378:metabolism; D015169:Colony Count, Microbial; D003470:Culture Media; D020563:Gammaproteobacteria / Q000254:growth & development* / Q000378:metabolism*; D005898:Glass; D008855:Microscopy, Electron, Scanning; D012623:Seawater / Q000382:microbiology*; D019354:Sodium Lactate / Q000378:metabolism; D013729:Terpenes / Q000378:metabolism; D014877:Water Pollution, Chemical
chemical_list: D003470:Culture Media; D013729:Terpenes; D002245:Carbon Dioxide; C014584:hexahydrofarnesylacetone; D019354:Sodium Lactate