Isolation of Mn(II)-oxidizing Bacteria

HMC 2010 short presentation Maren Emmerich

• Mn 2nd most abundant transition metal in Earth‘s crust• Mn redox cycling environmentally important• Mystery of microbial Mn2+ oxidation:

Not used for energy metabolism, why else?• 3 models of Mn2+-oxidizing bacteria:

- outer-membrane-associated multicopper-oxidases in Leptothrix discophora & 2 Pseudomonas putida strains - multicopper oxidase in marine Bacillus spores- marine -proteobacteria

Why? How? Results Ideas

• Mn 2nd most abundant transition metal in Earth‘s crust• Mn redox cycling environmentally important• Mystery of microbial Mn2+ oxidation:

Not used for energy metabolism, why else?• 3 models of Mn2+-oxidizing bacteria:

- outer-membrane-associated multicopper-oxidases in Leptothrix discophora & 2 Pseudomonas putida strains - multicopper oxidase in marine Bacillus spores- marine -proteobacteria

• Mn2+-oxidizers found in phylogenetically diverse groups

Why? How? Results Ideas

I) Sampling at Elkhorn Slough

Why? How? Results Ideas

II) Streak out 2 x 100 µl on K medium

• complex medium• enriched with 100 µM MnCl2

III) Aerobic incubation on labbench for 1-3 weeks…

Why? How? Results Ideas

Restreak brown colonies

Why? How? Results Ideas

Leucoberbelin blue test for MnO2

Why? How? Results Ideas

Some statistics• 34 samples from Kirby Park, Strawberry Mat, HMS beach• 10 plates with brown colonies after 1-3 weeks (AVG: 1.6)• 4 leucoberbelin positives after restreak• No isolate yet

Successful sampling sites

Kirby Park Kirby Park HMS beach

Why? How? Results Ideas

• Phylogeny of Mn2+-oxidizers? Sequence 16S rRNA genes of positive colonies

• Do isolates grow in liquid? Under which conditions? Inoculate minimal media and add different

electron donors & acceptors, incubate +/- light…

• Energetical benefit of Mn2+ oxidation? Compare growth yields of isolates grown +/- manganese

• More ideas?

G GggggGg

Thank you!

2H++ 2e- H2 -0.42 NAD+ + 2H+ + 2e- NADH + H+ -0.32 S + 2H+ + 2e- H2S -0.274 SO4

-2 + 8H+ + 8e- H2S -0.22 pyruvate + 2H+ + 2e- lactate -0.185 FAD + 2H+ + 2e- FADH + H+ -0.18 cytochrome b (Fe3+) + e- cytochrome b (Fe+2) 0.075 ubiquinone + 2H+ + 2e- ubiquinone H2 0.10 cytochrome c (Fe+3) + e- cytochrome c (Fe+2) 0.254 NO3

- + 2H+ + 2e- NO2- + H2O 0.421

NO2- + 8H+ + 6e- NH4 0.44

Fe+3 + e- Fe+2 0.771O2 + 4H+ + 4e- 2H2O 0.815

Why? How? Results Idea

Standard redox potentials at pH = 7

• Reaction: Mn2+ + 0.5 O2 + H2O → MnO2 + 2H+

• G◦ = −80.8 kJ/mole; Mn E◦ = + 0.419 V