DISCOVERY OF THERMOPHILIC GREEN SULFUR BACTERIA IN TWO GEOTHERMAL LOCALITIES IN THE CENTRAL PHILIPPINES

 

This web page is under construction. For now, this site merely serves as a running storage of observation, data and ideas on acidic anoxygenic sulfidic thermal springs (AASTS) we are investigating from Palinpinon (Negros) and Tongonan (Leyte), Philippines. Our research is just starting, and involves collaboration between Dr. Donna Bedard (a microbiologist from the Department of Biology, Rensselaer Polytechnic Institute - RPI), Dr. Russ Manson (a numerical modeler from the Civil and Environmental Engineering Department, RPI), Mr. Hermes Ferrer (a geochemist from the Energy Development Corporation, Philippine National Oil Company) and myself (an isotope geochemist from the Department of Earth and Environmental Sciences, RPI).

Our research group is interested in characterizing anoxygenic phototrophic microbial communities in highly reducing acidic sulfidic thermal springs. We believe that thermophilic green sulfur bacteria have far broader habitats and greater temperature ranges than those that are currently known (only documented previously in the Rotorua and Lake Rotoiti areas of North Island, New Zealand, where mats of thermophilic Chlorobium were first discovered in 1986 and still exist). We therefore set out to search for green sulfur bacteria in other habitats.

We proceeded to search for green sulfur bacteria from Philippine hot springs on a "hunch". The combined conditions of low pH, high temperature, and elevated sulfide that are found in the Chlorobium mats of New Zealand provide a highly reducing totally anoxic environment that excludes the growth of most cyanobacteria and eukaryotes. Thus this is an ideal environment to study the type of ecosystems that support thermophilic anoxygenic phototrophic communities. We reasoned that the geochemistry of many Philippine hot springs are broadly similar to those in New Zealand where Chlorobium has been found, hence we decided to take a look. A brief sampling visit was conducted last summer, while I was visiting the University of the Philippines. At that time we were not in a logistical position to collect critical sulfur speciation and other aqueous geochemical data. Nevertheless, bulk geochemical data were gathered by limited field measurements (pH, T) and biannual spring monitoring data of Philippine National Oil Company (Table 1).

The following photos and Table from the field survey and sampling trip last July (2000) confirmed our "hunch". We discovered a second major occurrence of green sulfur bacteria in Philippine hot springs. Preliminary molecular analyses (with primers specific for green sulfur bacteria) and enrichment work on specimens collected from Tongonan and Palimpinon last summer revealed that at least five springs are extensively inhabited by thermophilic green sulfur bacteria (Table 1). We believe there will be more discoveries in the future.

 

Table 1.
Preliminary Results from Samples of Green Sulfur Bacterial (GSB) Mats in Philippine Hot Springs

Spring Site

T
° C

pH

GSB
16S rRNA
(PCR)

Field Description

Macroscopic & Microscopic Description of Sample

Ticala#1A Palimpinon, Negros

40

7

+

Hot spring monitoring record indicates pH=6.5 and high H2S. Olive green "granular" appearing thin green coat over a distinctly buff-colored "substrate" (not sediment) exposed when the green sample is collected.

Very fibrous, almost rubbery, and dark brown to black with some deep bright green (cyanobacteria color). 25X -- Fine fibrous material. Lots of it is dark brown/black particle. Some is a dark bright blue-green (cyano?) color. Also some non-fibrous clumpy material.

Ticala#2A Palimpinon, Negros

43

7

+

This is the 3rd picture displayed on our web page. Same as 1-A. Monitoring record indicates 7, and quick litmus paper check shows ~ 7.

Most of sample is black-grey fibrous material with some olive. Color. Also, esp. in liquid, dark blue-green (cyano?) cells. Deep blue-green fine filaments readily visible at 25X. Also deep brown/black fibrous mat (undermat?) and sediment particles?

Malaunay#1A Palimpinon, Negros

48

6 -7

+

Hot spring monitor record pH=6.0. Thick yellow orange (Fe oxide?) coating on sediment surface near source. Farther downstream is green growth that looks "filamentous".

Bright orange liquid with some granular material @400X. Bright orange material is not filamentous and therefore is not Chloroflexus. Could be mineral iron, cellular, or a mix. Also, some ovoid clear greenish cells.

Malaunay#1B Palimpinon, Negros

45

nm

 

Same as 1B, but sampled from a separate location where the green growth is not filamentous in appearance.

Olive-orange-brown granular liquid and fibrous material. 25X-- Again, orange non-filamentous material, but there are filamentous green phototrophs clearly visible. Under 400X looks like Oscillatoria. Also lots of small ovoid cells and a few much smaller filaments. Chloroflexus?

Palimpinon#3A Palimpinon, Negros

42

7

+

Monitor record shows last pH measured is 6.2. Sampling below 50 ° C, but the effluent is much hotter. Plenty of green "stuff" coating sediments at stream bottom and on sides of rocks. Highest H2S/SO4 record in Palimpinon field.

Thin fibrous dark green mat like a skin. Also some free cells. Dark blue-green appearance, but some "yellow" green too, (i.e. like Chlorobium) 400X. Many very fine long green filaments, Chloroflexus-like. Also, many short chains of phototrophs (3-8 cells) and some tiny unicells.

Palimpinon#3B Palimpinon, Negros

43?

7

+

Same as above, but different portion of downstream. The top picture on our webpage came from here. On record I said the T is 53 ° C, but I wonder if that was a slip.

Clumpy fibrous dark green with dark green liquid. Color similar to Chlorobium. Texture similar to that of Ticala sample. 400X -- much like P3A, but with lots of mineral material. Sediment?

Palimpinon#3C Palimpinon, Negros

53

6.5

+

On video record, I said hotter than 50 ° C.

Clumpy and dense dark green liquid. Had to remove with spatula. Could not grab with forceps. This looks and feels like Chlorobium. 400X -- Like P3B. Also has a larger segmented chain of phototrophs. Each cell is peanut-shaped.

Baok#8A Tongonan, Leyte

50

7 - 7.5

+

On video record, I said 45 ° C. The second picture on our webpage came from here.

Viscous grainy dark green liquid. When it settles, the top looks like cyano color, but the rest is darker -- looks like it could be Chlorobium. 400X- Lots of Synechoccocus-like cells. No filaments.

Kapakuhan#24 Tongonan, Leyte

> 60

< 5

+

Very sulfidic. Boiling spring, but sampled downstream, and I said < than 70 ° C in video. Pyrite grains at the bottom of the stream, but the green stuff is on the faces of the rocks, sometimes submerged.

Thick viscous liquid -- orange and dark green. Used whole sample. None going back to -80° C. 25X. Looks like sediment with some green clumps. 400X -- lot of Synechococcus-like cells, but also some much tinier Chlorobium-like cells.

Note: We also have phototrophic growth from the P#3A and K#24 samples in media that select for GSB.

PHOTOS: (http://ees2.geo.rpi.edu/abrajanoCourses/AASTS.html)