How to theme the page template for search results
You can use a template, eg, page--search.tpl.php which would match the path to search and anything under it, eg, search/node/term, or you could create one called page--search-node.tpl.php which wouldn't match just the search page itself, but only search results from nodes, or you could use a template suggestion inside a preprocess_page() hook, eg, something like

mymoduleortheme_preprocess_page(&amp;vars) {

  if (arg(0)=='search' &amp;&amp; arg(1) &amp;&amp; arg(2)) { // we are somewhere down in search/node/term or similar
    $vars['theme_hook_suggestions'][] = 'page_my_template_for_search_results';
  }
}


and then create a template file page-my-template-for-search-results.tpl.php.

In any case, http://drupal.org/node/1089656 has some great documentation on template suggestions in D7.