Esponjas

CMLS, Cell. Mol. Life Sci. 59 (2002) 410–416 1420-682X/02/030410-07 $ 1.50 + 0.20/0 © Birkhäuser Verlag, Basel, 2002

CMLS

Cellular and Molecular Life Sciences

Roles of Bacillus endospores in the environment
W. L. Nicholson Department of Veterinary Science and Microbiology, University of Arizona, Tucson, Arizona 85721 (USA), Fax +1 520 621 6366, e-mail: WLN@u.arizona.edu Abstract. Theoccurrence and diverse roles of Bacillus spp. and their endospores in the environment is reviewed, with particular emphasis on soil ecology, host-symbiont and host-parasite interactions, and human exploitation of spores as biological control agents and probiotics.

Key words. Bacillus spp.; ecology; endospore; environment; pathogenesis; symbiosis.

Introduction The independent discoveries of thebacterial spore by Tyndall, Koch and Cohn in the last quarter of the 19th century [1–3] marked the beginning of the movement of spore research from the environment into the laboratory. With few exceptions, the laboratory is still where the bulk of spore research has been performed during the past 120 years, and within the past 40 years spore research has focused progressively more narrowly uponthe descendents of a particular strain of one bacterial species, Bacillus subtilis strain 168 [4]. Slepecky and Leadbetter [5] best described the prevailing situation in spore research as follows: ‘As a result of such attention we are by now aware of many exciting details regarding the physiology, biochemistry, and, now, molecular biology of endospore formation and germination. However, we are farless cognizant of the roles that endospore-forming organisms play in natural habitats’ [5]. Sporeforming bacteria indeed exhibit a bewildering array of environmental niches and habits, few of which have been explored in detail (reviewed in [4, 5]). In this brief review I will concentrate upon spores of Bacillus spp., the bacteria about which we possess the most information. I will make an attemptto consider the environmental roles of Bacillus spores in the context of a few broad basic ecological themes such as niche occupancy, competition, symbiosis, parasitism and human exploitation.

Roles of spores in natural settings Spores as time capsules In considering the question, What is the role of Bacillus spores in the environment? a simple and obvious answer immediately presents itself –to preserve and to propagate the genetic information contained within the bacterium. Based on the well-known practice of inducing sporulation in the laboratory by nutrient limitation, it is generally accepted that spore formation evolved as a mechanism for both spatial and temporal escape from local conditions unfavorable to rapid growth [4]. (The elaborate molecular mechanisms underlying sporelongevity and survival in the environment have recently been reviewed extensively [4 and references therein], and will not be reconsidered here.) As a device for preserving and dispersing genetic information in the environment, the spore is an incredible success. Spores can be found in environmental samples obtained from virtually all parts of both the Earth’s surface and subsurface [4, 6]. Reportsof the recovery of spores from environmental samples ranging in age from decades to hundreds of thousands of years are common [4, 7], and the scientific world has recently been treated to more controversial reports of spore longevity spanning geologic time scales. In 1994 and 1995 there appeared reports that viable Bacillus spp. spores had been isolated from the gut of a bee fossilized in Dominicanamber for an astounding 25–40 million years [8, 9]. Even this incredible age for a spore has been dwarfed by the report in 2000 of the discovery of Bacillus species 2-9-3, which was recovered from a brine inclusion within a 250 million-year-old salt crystal from the Permian Salado

CMLS, Cell. Mol. Life Sci.

Vol. 59, 2002

Multi-author Review Article

411

Formation near Carlsbad,...