Increasing Representation of Cultured Isolates

Methods to increase the representation of cultured microbial isolates from permafrost have recently been applied. For example, Vishnivetskaya et al. (2000) used natural permafrost sediment (NPS) enrichment to recover microbial isolates. NPS, consisting

Table 5.2 Phylogenetic groups of Bacteria cultured from permafrost8

Spits-

bergen

Chinese

Canadian

Siberian

Island

Antarctic

alpine

Alaskan

Phylogenetic

high Arctic

perma-

Siberian

perma-

perma-

perma-

ice

group

permafrost┬╗

frostc

cryopegd

froste

frostf

frostg

wedgeh

Actinobacteria

Arthrobacter

+

+

+

+

+

+

+

Brachybacterium

+

+

+

Cellulomonas

+

+

+

Cryobacterium

+

+

Frigoribacterium

+

+

Kocuria

+

+

Leifsonia

+

+

Microbacterium

+

+

+

+

Micrococcus

+

+

+

+

Nocardia

+

+

Promicromonospora

+

+

Rhodococcus

+

+

+

+

+

+

+

Streptomyces

+

+

+

unique genera

-

1

1

10

-

5

-

CFB

Flavobacterium

+

+

+

Pedobacter

+

+

+

unique genera

-

2

1

1

-

1

-

Firmicutes

Bacillus

+

+

+

+

+

+

Exiguobacterium

+

+

Paenibacillus

+

+

+

+

Planococcus

+

+

+

+

Planomicrobium

+

+

Sporosarcina

+

+

+

unique genera

3

-

-

-

-

2

1

Proteobacteria

Aeromonas

+

+

Myxococcus

+

+

Psychrobacter

+

+

+

Pseudomonas

+

+

+

+

+

+

unique genera

1

9

1

5

1

7

1

aGenera represented in at least two permafrost environments are indicated (+). The number of genera that were unique to the distinct permafrost environments are also indicated. Bacteria phyla are shown in bold

cShi et al. (1997), Vorobyova et al. (1997) and Vishnivetskaya et al. (2006) dBakermans et al. (2003) and Gilichinsky et al. (2005) eHansen et al. (2007)

fVorobyova et al. (1997) and Gilichinsky et al. (2007) gBai et al. (2006) and Zhang et al. (2007) hKatayama et al. (2007)

of thawing permafrost at 4┬░C and incubating the permafrost samples for up to 12 weeks before direct plating, increased the recovery of both the numbers and diversity of viable cells from most permafrost samples. Similarly, preliminary incubation in anaerobic and aerobic liquid media prior to plating greatly increased the recovery and diversity of recovered organisms from deep Greenland ice core samples and a Spitsbergen Island permafrost sample (Miteva et al. 2004; Hansen et al. 2007). Preliminary incubations may permit damaged, stressed, or dormant cells to repair damage induced by long-term exposure to thermal, osmotic, and nutritional stresses imposed by permafrost environments. Ideally, osmoprotectants such as salts, alcohols, and/or sugars could be incorporated in culture media, not only to enhance cellular survival and recovery, but to lower the freezing point of culture media to ambient permafrost temperatures. The ability to isolate and culture permafrost microorganisms at in situ temperatures will be crucial in determining the cellular mechanisms and physiological adaptations required for indigenous microbes to survive in permafrost.

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