Limits...
Portrait of a Geothermal Spring, Hunter's Hot Springs, Oregon.

Castenholz RW - Life (Basel) (2015)

Bottom Line: All of these demarcations are easily visible in the field.In addition, there is a biosulfide production in some sections of the springs that have a large impact on the microbiology.Most of the temperature and chemical limits have been explained by field and laboratory experiments.

View Article: PubMed Central - PubMed

Affiliation: Institute of Ecology and Evolution, University of Oregon, Eugene, OR 97403, USA. rcasten@uoregon.edu.

ABSTRACT
Although alkaline Hunter's Hot Springs in southeastern Oregon has been studied extensively for over 40 years, most of these studies and the subsequent publications were before the advent of molecular methods. However, there are many field observations and laboratory experiments that reveal the major aspects of the phototrophic species composition within various physical and chemical gradients of these springs. Relatively constant temperature boundaries demark the upper boundary of the unicellular cyanobacterium, Synechococcus at 73-74 °C (the world-wide upper limit for photosynthesis), and 68-70 °C the upper limit for Chloroflexus. The upper limit for the cover of the filamentous cyanobacterium, Geitlerinema (Oscillatoria) is at 54-55 °C, and the in situ lower limit at 47-48 °C for all three of these phototrophs due to the upper temperature limit for the grazing ostracod, Thermopsis. The in situ upper limit for the cyanobacteria Pleurocapsa and Calothrix is at ~47-48 °C, which are more grazer-resistant and grazer dependent. All of these demarcations are easily visible in the field. In addition, there is a biosulfide production in some sections of the springs that have a large impact on the microbiology. Most of the temperature and chemical limits have been explained by field and laboratory experiments.

No MeSH data available.


(a) Hunter’s pool at 9:25 am in April (~40 °C) with Geitlerinema terebriformis/Oscillatoria princeps cover (dark brown) but showing small patches of Beggiatoa leptomitiformis below the surface cover. Ostracods absent (Figure 2B in [18]); (b) Hunter’s pool at ~40 °C at 7:00 am (before sunrise, same day in April. Beggiatoaleptomitiformis (white) has migrated to the surface (complete darkness), with O2-sulfide interface 0.2–0.3 mm below surface of mat, and covering the Geitlerinema terebriformis below (Figure 2C in [18]).
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life-05-00332-f017: (a) Hunter’s pool at 9:25 am in April (~40 °C) with Geitlerinema terebriformis/Oscillatoria princeps cover (dark brown) but showing small patches of Beggiatoa leptomitiformis below the surface cover. Ostracods absent (Figure 2B in [18]); (b) Hunter’s pool at ~40 °C at 7:00 am (before sunrise, same day in April. Beggiatoaleptomitiformis (white) has migrated to the surface (complete darkness), with O2-sulfide interface 0.2–0.3 mm below surface of mat, and covering the Geitlerinema terebriformis below (Figure 2C in [18]).

Mentions: Below ~40 °C, in many of the mats in pools, rather than streams, a species of sulfide-oxidizing, filamentous, non-photosynthetic bacterium occurred. The gliding trichomes of Beggiatoa cf.leptomitiformis, migrated upward within the mat at nighttime (Figure 17), Nelson and Castenholz [19]. Although this strain of B. leptomitiformis oxidized sulfide and deposited S0 “internally”, the benefit was apparently, that of sulfide detoxification [29], since this species is, in fact, a chemoheterotroph, in which acetate is a favored substrate [21]. Ostracods were absent in these pools, probably because of inhibition by the higher sulfide, therefore, allowing a complete G. terebriformis top cover of the mat in daytime, mixed with Oscillatoria princeps [30] and Figure 17a, but at night is partially covered by the upward moving B. leptomitiformis population (Figure 17b). It was shown that B. leptomitiformis motility is negatively affected by high light and that its lower position in the mat in daytime is a result of a negative step-up photo-phobic response [19]. At night there was an aerotactic movement toward the O2 at the surface of the mat [29], Figure 17b. The G. terebriformis/O. princeps population formed a cover in moderate light intensity in daytime. At night, in this scenario, the cyanobacteria remained in position, possibly because of the sulfide inhibition of gliding motility [18,31,32].


Portrait of a Geothermal Spring, Hunter's Hot Springs, Oregon.

Castenholz RW - Life (Basel) (2015)

(a) Hunter’s pool at 9:25 am in April (~40 °C) with Geitlerinema terebriformis/Oscillatoria princeps cover (dark brown) but showing small patches of Beggiatoa leptomitiformis below the surface cover. Ostracods absent (Figure 2B in [18]); (b) Hunter’s pool at ~40 °C at 7:00 am (before sunrise, same day in April. Beggiatoaleptomitiformis (white) has migrated to the surface (complete darkness), with O2-sulfide interface 0.2–0.3 mm below surface of mat, and covering the Geitlerinema terebriformis below (Figure 2C in [18]).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4390855&req=5

life-05-00332-f017: (a) Hunter’s pool at 9:25 am in April (~40 °C) with Geitlerinema terebriformis/Oscillatoria princeps cover (dark brown) but showing small patches of Beggiatoa leptomitiformis below the surface cover. Ostracods absent (Figure 2B in [18]); (b) Hunter’s pool at ~40 °C at 7:00 am (before sunrise, same day in April. Beggiatoaleptomitiformis (white) has migrated to the surface (complete darkness), with O2-sulfide interface 0.2–0.3 mm below surface of mat, and covering the Geitlerinema terebriformis below (Figure 2C in [18]).
Mentions: Below ~40 °C, in many of the mats in pools, rather than streams, a species of sulfide-oxidizing, filamentous, non-photosynthetic bacterium occurred. The gliding trichomes of Beggiatoa cf.leptomitiformis, migrated upward within the mat at nighttime (Figure 17), Nelson and Castenholz [19]. Although this strain of B. leptomitiformis oxidized sulfide and deposited S0 “internally”, the benefit was apparently, that of sulfide detoxification [29], since this species is, in fact, a chemoheterotroph, in which acetate is a favored substrate [21]. Ostracods were absent in these pools, probably because of inhibition by the higher sulfide, therefore, allowing a complete G. terebriformis top cover of the mat in daytime, mixed with Oscillatoria princeps [30] and Figure 17a, but at night is partially covered by the upward moving B. leptomitiformis population (Figure 17b). It was shown that B. leptomitiformis motility is negatively affected by high light and that its lower position in the mat in daytime is a result of a negative step-up photo-phobic response [19]. At night there was an aerotactic movement toward the O2 at the surface of the mat [29], Figure 17b. The G. terebriformis/O. princeps population formed a cover in moderate light intensity in daytime. At night, in this scenario, the cyanobacteria remained in position, possibly because of the sulfide inhibition of gliding motility [18,31,32].

Bottom Line: All of these demarcations are easily visible in the field.In addition, there is a biosulfide production in some sections of the springs that have a large impact on the microbiology.Most of the temperature and chemical limits have been explained by field and laboratory experiments.

View Article: PubMed Central - PubMed

Affiliation: Institute of Ecology and Evolution, University of Oregon, Eugene, OR 97403, USA. rcasten@uoregon.edu.

ABSTRACT
Although alkaline Hunter's Hot Springs in southeastern Oregon has been studied extensively for over 40 years, most of these studies and the subsequent publications were before the advent of molecular methods. However, there are many field observations and laboratory experiments that reveal the major aspects of the phototrophic species composition within various physical and chemical gradients of these springs. Relatively constant temperature boundaries demark the upper boundary of the unicellular cyanobacterium, Synechococcus at 73-74 °C (the world-wide upper limit for photosynthesis), and 68-70 °C the upper limit for Chloroflexus. The upper limit for the cover of the filamentous cyanobacterium, Geitlerinema (Oscillatoria) is at 54-55 °C, and the in situ lower limit at 47-48 °C for all three of these phototrophs due to the upper temperature limit for the grazing ostracod, Thermopsis. The in situ upper limit for the cyanobacteria Pleurocapsa and Calothrix is at ~47-48 °C, which are more grazer-resistant and grazer dependent. All of these demarcations are easily visible in the field. In addition, there is a biosulfide production in some sections of the springs that have a large impact on the microbiology. Most of the temperature and chemical limits have been explained by field and laboratory experiments.

No MeSH data available.