title: In situSpectroscopy Reveals that Microorganisms in Different Phyla Use Different Electron Transfer Biomolecules to Respire Aerobically on Soluble Iron.
abstract: Absorbance spectra were collected on 12 different live microorganisms, representing six phyla, as they respired aerobically on soluble iron at pH 1.5. A novel integrating cavity absorption meter was employed that permitted accurate absorbance measurements in turbid suspensions that scattered light. Illumination of each microorganism yielded a characteristic spectrum of electrochemically reduced colored prosthetic groups. A total of six different patterns of reduced-minus-oxidized difference spectra were observed. Three different spectra were obtained with members of the Gram-negative eubacteria.Acidithiobacillus, representing Proteobacteria, yielded a spectrum in which cytochromesaandcand a blue copper protein were all prominent.Acidihalobacter, also representing the Proteobacteria, yielded a spectrum in which both cytochromeband a long-wavelength cytochromeawere clearly visible. Two species ofLeptospirillum, representing the Nitrospirae, both yielded spectra that were dominated by a cytochrome with a reduced peak at 579 nm.SulfobacillusandAlicyclobacillus, representing the Gram-positive Firmicutes, both yielded spectra dominated bya-type cytochromes.AcidimicrobiumandFerrimicrobium, representing the Gram-positive Actinobacteria, also yielded spectra dominated bya-type cytochromes.AcidiplasmaandFerroplasma, representing the Euryarchaeota, both yielded spectra dominated by aba3-type of cytochrome.MetallosphaeraandSulfolobus, representing the Crenarchaeota, both yielded spectra dominated by the same novel cytochrome as that observed in the Nitrospirae and a new, heretofore unrecognized redox-active prosthetic group with a reduced peak at around 485 nm. These observations are consistent with the hypothesis that individual acidophilic microorganisms that respire aerobically on iron utilize one of at least six different types of electron transfer pathways that are characterized by different redox-active prosthetic groups.In situabsorbance spectroscopy is shown to be a useful complement to existing means of investigating the details of energy conservation in intact microorganisms under physiological conditions.
authors.affiliation: College of Pharmacy, Xavier University of Louisiana, New Orleans LA, USA.
authors.forename: Robert C
authors.initials: RC
authors.lastname: Blake Ii
authors.affiliation: College of Pharmacy, Xavier University of Louisiana, New Orleans LA, USA.
authors.forename: Micah D
authors.initials: MD
authors.lastname: Anthony
authors.affiliation: College of Pharmacy, Xavier University of Louisiana, New Orleans LA, USA.
authors.forename: Jordan D
authors.initials: JD
authors.lastname: Bates
authors.affiliation: Department of Biology, Xavier University of Louisiana, New Orleans LA, USA.
authors.forename: Theresa
authors.initials: T
authors.lastname: Hudson
authors.affiliation: Department of Biology, Xavier University of Louisiana, New Orleans LA, USA.
authors.forename: Kamilya M
authors.initials: KM
authors.lastname: Hunter
authors.affiliation: Department of Biology, Xavier University of Louisiana, New Orleans LA, USA.
authors.forename: Brionna J
authors.initials: BJ
authors.lastname: King
authors.affiliation: Department of Biology, Xavier University of Louisiana, New Orleans LA, USA.
authors.forename: Bria L
authors.initials: BL
authors.lastname: Landry
authors.affiliation: Department of Biology, Xavier University of Louisiana, New Orleans LA, USA.
authors.forename: Megan L
authors.initials: ML
authors.lastname: Lewis
authors.affiliation: College of Pharmacy, Xavier University of Louisiana, New Orleans LA, USA.
authors.forename: Richard G
authors.initials: RG
authors.lastname: Painter
keywords: aerobic respiration on iron; chemolithotrophic bacteria; cytochromes; electron transport chains; in situ spectroscopy