Promotionskolloquium Rita Dunker 15. December 2010 Motility of the giant sulfur bacteria Beggiatoa in the marine environment

Promotionskolloquium

Rita Dunker15. December 2010

Motility of the giant sulfur bacteria Beggiatoa in the marine environment

General Introduction

Temperature response of gliding motility in Beggiatoa

Patterns of gliding motility in Beggiatoa

Summary & Outlook

Outline1

The Genus Beggiatoa

-Proteobacteria

Large, multicellular filaments

Form mats on soft sediment surface or live within the sediment

Store elemental sulfur (S0) in the cytoplasm

Oxidize reduced sulfur compounds with oxygen or nitrate

Auto- or heterotrophic nutrition

→ Link the S-, N- and C-cycle of sediments

Introduction

From

Tesk

e a

nd

Nels

on

, 2

00

6

Small marine Beggiatoa

Freshwater Beggiatoa

Vacuolate sulfur bacteria(Large marine Beggiatoa, Thioploca, Thiomargarita)

1 cm

50 µm

2

Habitats of Beggiatoa:

Coastal environments:

Sediments of bays, fjords, inter- and subtidal zone

Organic material

Photosynthetic microbial mats

and deep sea hotspots like

Seepage areas (cold seeps, mud volcanos..)

Geothermally active areas

Whale falls

Introduction T response Motility patterns Summary

Imag

e c

ou

rtesy

of

Han

s R

øy

© A

WI/I

frem

er

5 cm

3

Sediments with Beggiatoa occurrence

Soft sediment

Opposing gradients of oxygen and sulfide

Sediment surface if oxygen and sulfide overlap

Suboxic zone if oxygen and sulfide are separated

→ Habitats with fluctuating conditions

→ Beggiatoa constantly need to reorient in their environment

Red

raw

n f

rom

D

un

ker,

20

05

Red

raw

n f

rom

Jø

rgen

sen

et

al. 2

01

0

Introduction T response Motility patterns Summary4

→ Gliding motility is crucial for the positioning of the filament in the environment

→ Tactic responses provide cues for the directed movement

Oxic

Anoxic

1 mm

From

Lark

in a

nd

Hen

k,

19

96

Motility in Beggiatoa

Locomotion by slime extrusion through pores

Tactic responses to chemical and physical stimuli


From: Møller et al. 1985

Oxic

Anoxic

5

Beggiatoa mat on the sediment surface

45% → 95% air saturation, 40 h, 30 fps


1 cm1 cm

1 cm

45% air sat. 95% air sat.

Questions

Does temperature control the gliding speed of Beggiatoa ?

Is the speed of gliding motility adapted to the prevailing temperature of different climatic locations?

What is the acclimatisation potential of gliding speed to changing temperatures?

Temperature response of gliding motility7

Background

Beggiatoa occur at all climates:

Permanently cold, temperate, tropical

Oftentimes seasonally fluctuating temperatures

Growth and metabolism are temperature dependent, how about gliding motility?

Minimum Temperatur

e

Optimum Temperatur

e

Maximum Temperatur

e


Mod

ified

aft

er

Dale

et

al.

20

08

Annual temperature in 2004

275

280

290

TSWI

(K)

jan feb mar apr may jun jul aug sep oct nov dec

.

18°C

3°C

Methods:

Tropical, temperate and arctic filaments

Temperate filaments acclimatized to summer and winter conditions, respectively

Custom-made chamber for monitoring of gliding speed of single filaments

Temperature control by a thermostat


The temperature range for gliding


tropical temperate summer

temperate winter

arctic

Dunker et al. 2010

10

MotilityRespiration

from

Rid

gw

ay a

nd

Lew

in,

19

88

tropical temperate summer

temperate winter

arctic

Calculation of

Range for optimal physiological activity

Activation energy

Arrhenius equation


T range for gliding wider that range for optimal physiological activity

T in situ within the range for optimal physiological activity

Optimum T beyond the range for optimal physiological activity

Extended T range at winter conditions

RT

EA

alnln

Du

nke

r et

al.

20

10

T in situT opt

Response at the extreme ends of the temperature range

Filaments withstand transient freezing

Decrease in gliding speed at the cold end is reversible

Decrease in gliding speed at the warm end is irreversible


Arctic filaments

Temperate filaments

Conclusions:

Gliding speed regulated by T

Gliding is a physiologically regulated response

Gliding speed is adapted to the prevailing environmental T → ubiquitous distribution of Beggiatoa

Acclimatisation to seasonal T changes on a community scale


Motility patterns in Beggiatoa

Questions

Which gliding patterns do Beggiatoa filaments use to orient in their environment?

Can these patterns explain the Beggiatoa distribution in the suboxic zone?

14

Methods

Filaments in gradient agar tubes

Imaging setup with illumination and interval imaging option

Image analysis

Monitoring of

Single trails

Changes in gliding direction


Trails of filaments

Within the mat: Filaments „anchor“ at the overlap of oxygen and sulfide

Above and below the mat: Filaments glide long trails, move a net distance away from their origin

How?


Du

nke

r et

al. s

ub

mit

ted

Reversal patterns of filaments

Within the mat: Average distance is shorter than filament length

Above and below the mat: Average distance glided is longer than filament length

Filaments change reversal behaviour when gliding into the mat


Du

nke

r et

al. s

ub

mit

ted

17


Beggiatoa mat in an oxygen sulfide gradient, 4 h 30 min, 25 fps

Modeling Beggiatoa motility

Filament in the mat

Filament above and below the mat („random gliding“)


Can the model explain the observed Beggiatoa distribution in a photosynthetic mat with a diurnal migration pattern?


Red

raw

n f

rom

Hin

ck e

t al.

20

07

dusk dawn


→ 10 h of darkness is not enough to follow the migrating oxygen front

21

Modeled biomass distribution

Counted biomass distribution

Red

raw

n f

rom

Hin

ck e

t al.

20

07

dusk dawn

10 h dark cycle


Most random trails less than a day

Long random trails:

NO3- storage is

gradually depleted

Trail duration: several days

→ High biomass in the suboxic zone

→ High NO3- storage

capacity needed

NO3-NO3-NO3-NO3-NO3-NO3-NO3-NO3-NO3-

22

Beggiatoa distribution in the suboxic zone

Conclusion

Increase of reversal frequency keeps filaments at the oxic-anoxic interface

Long random trails can bring filaments back to the oxic-anoxic interface

High NO3- storage capacity fuels the long random trails in

the anoxic sediment

Phobic responses protect the filaments from gliding out of the suboxic zone


Summary and Outlook

Beggiatoa gliding speed underlies T control

→ mechanism of gliding?

Beggiatoa distribution in suboxic zone is in accordance with a phobic response to sulfide

→ nature of the response to sulfide?

→ role of sulfide in mat formation?

Reversal behavior

→ coordinated? cell-to-cell communication?


Thanks to:

Prof. Dr. Bo Barker Jørgensen

Dr. Hans Røy

Dr. Tim Ferdelman

Dr. Anja Kamp

Dr. Jan Fischer

Associate Prof. Dr. Lars Peter Nielsen (Uni Århus)

Dr. Peter Stief

Dr. Dirk de Beer

Dr. Heide Schulz-Vogt

Technical staff:

Electronic workshop

Mechanic workshop

Biogeochemistry group

Microsensor group

My colleagues from the Biogeochemistry group, family and friends

Thank you for your attention

Introduction T response Motility patterns Conclusion

From

: M

ølle

r et

al.

19

85

NO3-

S0

H2S SO42-

H+

Nitrate transport:

H+ translocation ATPase

H+ translocating pyrophosphatase

NO3-/H+ antiporter

Carbon metabolism:

Autotrophic or heterotrophic

Large marine strains: RubisCO

Sulfur utilisation:

H2S, S0, S2O3-

Poly-phosphate storage as by genomic data

Vacuole

Cytoplasm


Model of the gliding mechanism in

Myxobacteria Hydration of electrolyte gel

fibers

Gel expands and leaves through the opening of the pores

Yields enough propulsion force to explain gliding motility at the observed speed

Wolgemuth et al. 2002


The temperature range of physiological adaptation

Arrhenius function:

ln = ln A - Ea/RT

Arrhenius plots:

Calculation of the activation energy Ea

Ea gives an estimate of the T dependence of a reaction

Similar Ea to that of bacterial enzymatic processes from cold environments

tropicaltemperate summer

temperate winter arctic


Origin of filamentsT response of gliding speed

Tin situ

(°C)

Topt

(°C)

Ea (kJ

mol-1)Q10 source

Tropical Mesophilic 20 37 49 2.1 (19-29 °C) this study

Temperate Mesophilic 13 30 58 2.3 (12-22 °C) this study

Temperate (cold acclimatized)

Mesophilic 4 30 50 2.1 (8-18 °C) this study

Arctic Psychrotolerant 6.5 17 46 2.0 (0-10 °C) this study

Gliding motility of Beggiatoa alba

35.2 Crozier and Stier, 1926

Gliding motility of Oscillatoria

38.7 Crozier and Federighi,

1924

Gliding motility in Oscillatoria princeps

30-40 42 144a) Halfen and Castenholz, 1971

Gliding motility of Flexibacter polymorphus

35 61.13 2.06 (15-35 °C) Ridgway and Lewin, 1988

Respiration of Flexibacter polymorphus

40 58.62 2.64 (15-35 °C) Ridgway and Lewin, 1988


Average distances:

Do individual reversal frequencies match the mat position?

Within the mat: Filaments glide shorter distances

Above and below the mat: Filaments glide longer distances


Motility in Beggiatoa below the mat- a random walk?

Diffusion coefficient D of a filament below the mat:

tD 4 L

t 4/L D 2

Filaments without a cue move as by a random walk


Solid line: Distance moved away from the origin as observed in a real filament

Dashed line: Distance of a particle diffusing at the D of a Beggiatoa filament

Dotted line: Distance moved away from the origin of a modeled Beggiatoa filament


• Nitrate storage: 270 mM• Nitrate consumption: 13 mM/day → lasts 21 days



Can the model help to explain the distribution pattern of Beggiatoa in the suboxic zone?

Known parameters of coastal sediment from Århus Bay

Frequency analysis plot:

Most random trails less than a day

Time spend on random trails: on average 10 days

→ Duration of random trails depends on NO3

- storage

Du

nke

r et

al. s

ub

mit

ted


Reversal behavior of Beggiatoa

10 µm

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Promotionskolloquium Rita Dunker 15. December 2010 Motility of the giant sulfur bacteria Beggiatoa in the marine environment